Hole-doped maganite with middle to narrow bandwidth La1-xCaxMnO3 was extensively studied because of its colossal magnetoresistance (CMR) characteristic under a magnetic field. These kind of materials show un- common magnetic and electric properties. The charge order phase only happens to the region x> 0.5, and along with decreasing temperature, its phase goes from para-insulator to charge-ordered then to antiferromagne- tism. In our studies, we apply correlation function of Green¡¦s function to LCMO and get susceptibility of charge and spin. Then we can get the cri- tical value of Coulomb repulsion inside the material by substituting the experimental values of phase transition temperature. This critical values is the key point of charge-ordered. Then we can also get the size of char- ge gap which decides the stability of charge-ordered phase. After know- ing the Coulomb repulsion and charge gap, we can picture the relation of inside and on-site Coulomb repulsion qualitatively while the transition happens. Here the on-site Coulomb repulsion means to the Hund¡¦s coupl- ing between d electrons. And by this we¡¦ll understand the physics inside CMR materials.

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xxv, 207 p. ; ill. (some col.) A print copy of this title is available from the UO Libraries, under the call number: SCIENCE QD172.T6 T87 2008 / A growing interest in the physics of complex systems such as in the transition-metal oxide family has exploded recently, especially in the last 20 years or so. One notable effect is the change in electrical resistivity of a system by orders of magnitude in an applied magnetic field, coined the "colossal magnetoresistance effect". In efforts to understand these types of effects, there has been an unveiling of a rich variety of phenomena in the field of strongly correlated electron physics that has come to dominate the current scientific times. Most notable is the competition of myriad types of order: magnetic, lattice, charge and orbital all self-organize to display a fascinating array of phases on a variety of length scales. Furthermore, it has become apparent that new probes are needed to grasp some of this physics that transcends current condensed matter theory, where much of the behavior of these types of systems has remained unexplored. We have developed a new technique to gain more information about the system than with conventional x-ray diffraction. By scattering highly coherent, low energy x-rays, we can measure manganite speckle: a "fingerprint' of the microscopic structure in the bulk. The coherence of the x-rays can further be used to elucidate new insight into the dynamics of these phases. We describe here a number of novel effects near the orbital order phase transition in a half-doped manganite. We observe a small fluctuating component in the scattered signal that is correlated with three effects: both a rapidly decreasing total signal and orbital domain size, as well as an abrupt onset of a broad background intensity that we attribute to the thermal production of correlated polarons. Our results suggest that the transition is characterized by a competition between a pinned orbital domain topology that remains static, and mobile domain boundaries that exhibit slow, spatiotemporal fluctuations. This study opens up a new chapter to the study of manganite physics as coherent x-ray scattering offers a new direction to understand the strange and exotic behavior demonstrated in the multifaceted manganites. / Adviser: Stephen Kevan

No description available.

Pagrindiniai bėgių tipo elektromagnetinių svaidyklių technologijos uždaviniai yra susiję su daugybe fizikinių reikinių, vykstančių sviedinio kontaktų sąlyčio su bėgiais riboje. Todėl elektromagnetinių procesų, atsirandančių dėl didelių elektros srovės tankių ir slydimo greičių tyrimas yra svarbus šios srities uždavinys. Dėl magnetinės difuzijos ir greito sviedinio judėjimo, srovė koncentruojasi galinėje kontakto dalyje, kuri dėl stipraus Joule šilimo greitai susidėvi, o tai apriboja svaidyklės efektyvumą. Disertacijoje pateikiami magnetinio lauko difuzijos tyrimai bėgių tipo svaidyklėse panaudojant specialius jutiklius magnetinių laukų matavimui. Šie nauji jutikliai, pagaminti iš plonų La0,83Sr0,17MnO3 sluoksnių, pasižyminčių milžiniškos magnetovaržos (MM) reiškiniu (MM-B-skaliariniai jutikliai), buvo pritaikyti svaidyklėse, veikiančiose statiniame ir dinaminiame režime, esant dideliems elektromagnetinių triukšmų lygiams ir mechaniniams įtempiams. Darbo metu buvo nustatyta, jog šiais jutikliais galima išmatuoti stipraus magnetinio lauko impulso amplitudę, kai nėra žinoma šių laukų kryptis. Buvo ištirti nevienalyčių magnetinių laukų pasiskirstymai bėgiuose, atsirandantys dėl artumo efekto bei greičio skinefekto, sviediniui judant greičiau nei 1500m/s. Bandymai su įtvirtintu daugelio šepetėlių konstrukcijos sviediniu parodė, kad priekiniai šepetėliai, dėl nepakankamo Lorenco jėgos sukuriamo slėgio, gali pararasti elektrinį kontaktą su bėgiais. / The development of rails and armatures which ensure a sliding solid-to-solid contact during the whole projectile acceleration is a great challenge in the field of railgun technology. Multifaceted physics exists at the sliding contact interface: The current concentrates at the rear of the interface due to magnetic diffusion processes and the fast armature movement. Consequently, Joule heating leads to enhanced wear in this region. In this dissertation, magnetic diffusion in railguns is investigated by means of measuring magnetic fields with CMR-B-scalar sensors at static and dynamic experimental conditions. These novel sensors, based on La0.83Sr0.17MnO3 thin films exhibiting colossal magnetoresistance were adapted for the use at railguns. It was found that these sensors are effective tools to measure the magnitude of high pulsed magnetic fields independent of the field orientation. Magnetic field distributions influenced by proximity and velocity skin effect could be measured in the harsh railgun environment. The obtained results allowed to estimate the skin depth in the rails at the sliding interface of a fast moving armature (>1500m/s). Furthermore experiments with fixed multiple brush armatures showed that front brushes can have contact problems in case of missing contact pressure.

In this thesis, we have performed systematical study of anomalous electric and magnetic behaviors of the 3d transition metal oxides; colossal magnetoresistance (La1−xRxMnO3 where R is a divalent alkaline earth ion) and Multiferroic (Ho1-xLaxMn2O5) systems by X-ray and Neutron scattering techniques. In our study, the enhancement of the transfer temperature for La0.8Ba0.2MnO3 under strain effect from the SrTiO3 substrate could be possible due to two reasons which one is Sr diffusion from SrTiO3 substructure, and other one is the octahedral MnO6 high symmetry are increasing. We focus the intrinsic strain effect on La0.67Ca0.33MnO3 and La0.8Ba0.2MnO3 films, and findings show that due to the different ionic sizes of doped Ca or Ba ions, the strain effect acts differently in the way it deforms. The interfacial strain effect produces opposite influences on the lattice symmetry, the average Mn¡VO bond lengths, the average oxygen disorders, the coupling symmetries inside and in the vicinity of the MnO6 octahedrons, as well as producing an opposing trend in metal-insulator and magnetic transition temperatures of the strained La0.67Ca0.33MnO3 and La0.8Ba0.2MnO3 films. The strain effects on the electronic structures of La0.67Ca0.33MnO3 and La0.8Ba0.2MnO3 thin films have been studied by O K-edge x-ray absorption near edge structure (XANES) spectroscopy. For La0.67Ca0.33MnO3, the first-principles calculations reveal that the features in the XANES spectra are associated with hybridized states between O 2p and Mn minority-spin 3d t2g and eg, La 5d/Ca 3d, and Mn 4s/Ca 4p states. An analysis of these features shows that the tensile strain decreases substantially La¡VO and Ca¡VO hybridization and TC for La0.67Ca0.33MnO3. For La0.8Ba0.2MnO3, the small compressive strain enhances slightly La¡VO and Ba¡VO hybridization and TC. In this thesis, the influence of the local structure distortion on the magnetic transition in La doped HoMn2O5 Multiferroics has been investigated systematically. The orthorhombic crystal structure of Ho1−xLaxMn2O5 is maintained up to x¡Ø0.2 but decomposed into multiphase for x¡Ù0.25. By doping La ions to a concentration of 0.1¡Øx¡Ø0.2, the formation of the RMnO3 1(13) phase can be suppressed and single-phase Ho1−xLaxMn2O5 (0.1¡Øx¡Ø0.2) compounds can be formed under 1 atm flowing oxygen. For x=0.2, a ferromagnetic FM transition at 150 K is superimposed on the paramagnetic background, which implies that the compound undergoes a ferromagnetic to antiferromagnetic (AFM) transition. This unique FM to AFM transition is observed for the first time. The FM transition is attributed to the formation of magnetic clusters in a host paramagnetic matrix. The anomalous magnetic clusters phenomena observed in Ho0.8La0.2Mn2O5 can be directly attributed to the different properties between Ho and La ions, and the differences of Ho and La ions are not only in the ionic radius but also in the electron negativity. During 90~150K, X-ray scattering diffraction presented the new addition peaks indicates the new electric density distribution, and the Neutron powder scattering diffraction (NPD) refining results show that the local structure of R-O (R: La, Ho) is un-symmetry which is conflict to the La Extended X-ray absorption fine structure (EXAFS) (which shows that the local structure of La-O becomes more symmetry than H-O. Since the refining values of the NPD are an average of entire crystal, such that it cannot tell the local changes. X-ray absorption spectrum (XAS) and EXAFS, in contrarily, can provide the local information. They implies that the temperature evolutions of the coupling strength with O 2p or unoccupied density state are opposite for the Ho and La ions in our Ho0.8La0.2Mn2O5 sample. Therefore, local change of ions position and charge redistribution happens in this specific temperature range.

The development of rails and armatures which ensure a sliding solid-to-solid contact during the whole projectile acceleration is a great challenge in the field of railgun technology. Multifaceted physics exists at the sliding contact interface: The current concentrates at the rear of the interface due to magnetic diffusion processes and the fast armature movement. Consequently, Joule heating leads to enhanced wear in this region. In this dissertation, magnetic diffusion in railguns is investigated by means of measuring magnetic fields with CMR-B-scalar sensors at static and dynamic experimental conditions. These novel sensors, based on La0.83Sr0.17MnO3 thin films exhibiting colossal magnetoresistance were adapted for the use at railguns. It was found that these sensors are effective tools to measure the magnitude of high pulsed magnetic fields independent of the field orientation. Magnetic field distributions influenced by proximity and velocity skin effect could be measured in the harsh railgun environment. The obtained results allowed to estimate the skin depth in the rails at the sliding interface of a fast moving armature (>1500m/s). Furthermore experiments with fixed multiple brush armatures showed that front brushes can have contact problems in case of missing contact pressure. / Pagrindiniai bėgių tipo elektromagnetinių svaidyklių technologijos uždaviniai yra susiję su daugybe fizikinių reikinių, vykstančių sviedinio kontaktų sąlyčio su bėgiais riboje. Todėl elektromagnetinių procesų, atsirandančių dėl didelių elektros srovės tankių ir slydimo greičių tyrimas yra svarbus šios srities uždavinys. Dėl magnetinės difuzijos ir greito sviedinio judėjimo, srovė koncentruojasi galinėje kontakto dalyje, kuri dėl stipraus Joule šilimo greitai susidėvi, o tai apriboja svaidyklės efektyvumą. Disertacijoje pateikiami magnetinio lauko difuzijos tyrimai bėgių tipo svaidyklėse panaudojant specialius jutiklius magnetinių laukų matavimui. Šie nauji jutikliai, pagaminti iš plonų La0,83Sr0,17MnO3 sluoksnių, pasižyminčių milžiniškos magnetovaržos (MM) reiškiniu (MM-B-skaliariniai jutikliai), buvo pritaikyti svaidyklėse, veikiančiose statiniame ir dinaminiame režime, esant dideliems elektromagnetinių triukšmų lygiams ir mechaniniams įtempiams. Darbo metu buvo nustatyta, jog šiais jutikliais galima išmatuoti stipraus magnetinio lauko impulso amplitudę, kai nėra žinoma šių laukų kryptis. Buvo ištirti nevienalyčių magnetinių laukų pasiskirstymai bėgiuose, atsirandantys dėl artumo efekto bei greičio skinefekto, sviediniui judant greičiau nei 1500m/s. Bandymai su įtvirtintu daugelio šepetėlių konstrukcijos sviediniu parodė, kad priekiniai šepetėliai, dėl nepakankamo Lorenco jėgos sukuriamo slėgio, gali pararasti elektrinį kontaktą su bėgiais.

Amostras policristalinas de La(5/8-y)Pr(y)Ca(3/8)MnO(3); 0 y 0.625; foram produzidas pelo método da mistura estequiométrica de óxidos e tratadas termicamente ao ar a 1400 oC. As amostras foram caracterizadas através de medidas de difração de raios-X, resistividade elétrica rho(T), susceptibilidade magnética chi(T) e magnetorresistividade rho(T, H = 50 kOe). Os resultados das análises dos diagramas de raios-X indicaram que os materiais são de fase única e que houve uma substituição efetiva de La por Pr no sítio A ao longo da série. Medidas de rho(T) e chi(T) revelaram que a temperatura de transição de fase metal-isolante TMI e temperatura de Curie TC decrescem com o aumento da concentração y e que a resistividade residual rho0 (rho(T = 10 K)) é consideravelmente alta em amostras com y 0.35. Ainda, com o decréscimo de T, as amostras com y 0.35 transitam para uma fase de ordenamento de carga em TOC ~ 194 K e, em seguida, para uma fase metálica em TMI. Essas medidas também sugerem a coexistência de fases ferromagnética-metálica FMM e de ordenamento de carga isolante OCI nesses materiais. Nas propriedades físicas macroscópicas, a fase FMM mostrou ser a dominante para os compostos com pequenas concentrações de Pr (y 0.25) e a fase OCI dominante para os compostos com altas concentrações de Pr (y 0.40). As medidas de rho(T, H = 50 kOe) mostram que a magnitude da resistividade elétrica decresce drasticamente nas vizinhanças de TMI sob a aplicação de um campo magnético externo. A magnitude de MR (MR = (rho(H = 0)-rho(H = 50 kOe))/rho(H = 50 kOe)) entre os extremos da série (y = 0 e 0.625) varia até sete ordens de grandeza, sendo que o máximo valor de MR para amostras com y = 0 é de ~ 0.75 e naquelas com y = 0.625 é ~ 3.4x106 . O diagrama de fases deste composto evidencia uma região crítica (0.30 y 0.40) onde os valores de TMI, TC, MR e 0 variam abruptamente como função de y, sendo que em outras regiões tal variação é mais suave. A variação significativa desses quatro valores indica uma competição mais forte entre as fases coexistentes ocorre na região crítica. Algumas características marcantes podem ser observadas nas amostras da região crítica tais como: a presença de um segundo pico, abaixo de TMI, em ~ 90 K e ~ 72 K na curva de rho(T) de amostras com y = 0.30 e 0.35, histerese térmica mais pronunciada em rho(T) e chi(T), MR torna-se colossal, relaxação significativa da resistividade elétrica com o tempo, entre outras. Assim, as propriedades de transporte e magnéticas nessa região crítica são dominadas pela forte competição entre as fases coexistentes. / Polycrystalline samples of La(5/8-y)Pr(y)Ca(3/8)MnO(3); 0 y 0.625; were synthesized by the solid-state reaction method and sintered in air at 1400 oC. These compounds were studied by measurements of X-ray powder diffraction, magnetic susceptibility chi(T), and electrical resistivity rho(T, H). X-ray powder diffraction measurements indicated single phase materials and an effective substitution of La by Pr. Results from rho(T) and chi(T) revealed that increasing y in this series results in a rapid reduction of both the insulator to metal transition temperature TMI and the Curie temperature TC. Such a rapid decrease in TMI with increasing y is also accompanied by the occurrence of a new transition temperature, termed TCO, which is related to the transition to the charge ordered CO state. Such a temperature, which is essentially independent of y, occurs at TCO ~ 194 K and is mainly observed in samples with y 0.35. The other feature is the presence of a large residual resistivity electrical rho(0 = (10 K)) for large y (y 0.35) at low-T even though rho(T) suggests a metallic behavior below TMI. The temperature for the maximum magnetoresistance effect occurs near TMI, that shifts to higher T with increasing field. The MR is defined here as (rho(H = 0)-rho(H = 50 kOe))/rho(H = 50 kOe) and is enhanced by seven orders of magnitude from ~ 0.75 up to ~ 3.4x106 in samples with y = 0 and y = 0.625, respectively. Some features like the thermal hysteresis observed in both rho(T) and chi(T) curves indicate the coexistence of different phases in a range of y concentration, i. e., the ferromagnetic-metallic FMM and the charge ordered-insulating COI domains. The FMM is stable for y 0.25, but the COI state becomes dominant for y 0.40. There is a critical region in the phase diagram, ranging from y = 0.30 to 0.40, where the magnitude of the TMI, TC, MR, and 0 were found to display abrupt changes with increasing y. Some anomalous features like a second peak in rho(T) below TMI, a two-step increasing in chi(T), a colossal MR effect and others are observed for compositions belonging to this critical region. Our combined data suggest that the general physical properties of these compounds in such a critical region are dominated by the strong competition between coexisting ferromagnetic-metallic and charge ordered-insulating phases.

Synthesis, nuclear structure, and magnetic properties of the perovskites: Nd0.7-xMgxSr0.3MnO3 (x=0.0, 0.1), Nd0.6Mg0.1Sr0.3Mn1-zMgzO3 (z=0.1, 0.2), LaCr1-yMnyO3 (y=0.0, 0.1, 0.2, 0.3) and La1-xNdxFe0.5Cr0.5O3 (x=0.1, 0.15, 0.2) have been studied. The structure of the samples was investigated by X-ray and Neutron powder diffraction and the magnetic properties were investigated by magnetization measurements using SQUID-magnetometry. All compounds have orthorhombic structure with spacegroup Pnma (No. 62). The compounds which had the composition Nd0.7Sr0.3Mn1-yMgyO3 by preparation, were found to attain the composition Nd0.7-xMgxSr0.3MnO3 and Nd0.6Mg0.1Sr0.3Mn1-zMgzO3. The x=0.0 and 0.1 compounds order in a pure ferromagnetic structure at about 200 K, but the Mn moments become slightly tilted and attain an antiferromagnetic component below 20 K. A ferromagnetic Nd moment also appears at low temperatures. The compounds with Mg substitution y=0.2 and 0.3 do not exhibit long range magnetic order, but local ferromagnetic correlations among the Mn moments appear below 200 K. At low temperature, also a local antiferromagnetic ordering of the Nd magnetic moments occurs. In these compounds, the Mn3+/Mn4+ ratio is reduced so that the double exchange interaction is suppressed and the antiferromagnetic superexchange interaction favoured. The samples of composition LaCr1-yMnyO3 have orthorhombic structure at room temperature and below. The magnetic properties of the system are markedly affected by Mn-substitution. The parent compound LaCrO3 is a pure G-type antiferromagnet with Néel temperature 290 K. With incresing Mn-substitution, a ferromagnetic component developes in the ordered phase bcause of canting of the magnetic moments. The degree of canting increases with increasing Mn-substitution and the magnitude of the antiferromagnetic component of the moment decreases. The system La1-xNdxFe0.5Cr0.5O3 has the same antiferromagnetic G-type structure as LaCrO3, but orders already at temperatures above 400 K and develops only a very weak ferromagnetic component of the magnetic moment at low temperatures.

Study of rare-earth manganites has been a very active research area in the last few years in condensed matter physics. This is due to the interesting phenomena such as (1) colossal magneto resistance (2) charge, orbital and spin ordering and (3) phase separation exhibited by these materials as a function of doping, pressure and temperature [1-3]. There is a lot of experimental data available in literature on different doped manganites, but no satisfactory and complete theoretical understanding is available yet. Though different theoretical models proposed are able to explain certain individual physical properties, a unified theory is missing which can comprehensively explain the full phase diagram. The study of such complex systems requires a probe that is sensitive to various interactions observed in manganites such as spin-spin interactions, spin-lattice interactions, spin-orbit interactions, crystal field interactions and the magnetic environment of the spins. Electron paramagnetic resonance (EPR) being sensitive to these interactions is an ideal probe for investigating these strongly correlated systems. A number of EPR studies have been reported in the paramagnetic phase of manganites, throwing light on the complex spin dynamics present in the manganites [4-10]. There are a few reports in the ferromagnetic state of manganites [11-12]. In recent years, a few studies reporting the observation of phase separation using EPR have also been published [13-15]. Charge ordering phase is the other interesting phase, which is not understood from EPR point of view [16-19]. Recently there are a few reports on suppression of CO phase by reducing the particle size from micro to nano range [20-22]. In this thesis we present the results of Electron Magnetic Resonance (EMR) (EPR in the paramagnetic phase and FMR: ferromagnetic resonance in the ferromagnetic phase) studies supported by magnetization and magneto-transport studies of the following : (1) various magnetic phases in the two electron doped manganite Ca1-xCexMnO3 (CCMO) (2) Charge ordered phase vs. ferromagnetic metallic phase as a function of Cr and Ni doping at the Mn site of Nd0.5Ca0.5MnO3 (NCMO) and comparison between the effect of the two dopants, and (3) a study of nano-sized particles (with different particle size) of Cr doped NCMO. Chapter 1 of the thesis consists of a brief introduction to the general features of manganites describing various phenomena and the interactions underlying them. Further we have written a detailed overview of EPR studies in manganites describing the current level of understanding in the area. In this chapter we have also described the experimental methodology and the analysis procedure adopted in this work. Chapter 2 reports the magnetization, transport and electron paramagnetic resonance studies (EPR) on two electron-doped manganites Ca1-xCexMnO3 (0.075 ≤ x ≤ 0.20). The various compositions of CCMO were prepared by solid-state synthesis and characterized by different techniques like XRD, SEM, EDX, and ICPAES. Our magnetization and transport results are consitent with the earlier reports [23-25]. For compositions x ≥ 0.13, all the EPR parameters viz. intensity, linewidth and the resonance field show signatures of a CO phase and at low temperature coexistence of two magnetic phases. x = 0.1 composition shows the most interesting results. Though the EPR intensity and resonance field indicate the presence of a CO phase, the EPR linewidth shows behaviour of a spin-disordered phase which we attribute to a possible spin-liquid phase [26]. The linewidth for x = 0.11 composition shows a combination of a CO and a spin-disorderd phase. For low composition x = 0.075, we observe a weak ferromagnetic phase and later on at low temperatures an antiferromagnetic phase. We do not observe the CO phase for this composition. In chapter 3, we present the magnetization, magnetotransport and EMR studies on Cr doped NCMO (0.0 ≤ x ≤ 0.10) [27]. The samples were prepared by solid-state synthesis and characterized by various techniques like XRD, SEM, EDX, and ICPAES. The magnetization studies show that the Cr doping induces ferromagnetic phase at low temperatures. With the increase of Cr doping the magnetization increases at the expense of the CO phase and for higher doping CO phase disappears completely. The Cr doping induces insulator-metal transition and with increase of Cr doping the metallic phase increases. The doped samples show high CMR, almost 100%, near the TC. The EMR studies in the paramagnetic phase indicate a CO phase for low Cr doping and the presence of short-range dynamical CO-OO correlations for higher Cr doping, which were not observed in magnetization studies. We observe two EPR signals at low temperatures for the Cr doped samples. For 3% doping, the two signals appear well above TC whereas for higher doping (5%, 10%) the two signals were observed in the FM phase. We rule out the possibility of the two-signal behaviour arising from the coexistence of two magnetic phases. For higher doping, the presence of two signals in FM phase can be attributed to magnetic anisotropy. With increase of Cr doping, magnetic anisotropy decreases which is also supported by reduction of magnetic anisotropy in magnetization measurements. But it cannot explain the observation of two signals above TC in the 3% doped sample. In chapter 4, we present the magnetization, magnetotransport and EMR studies on Ni doped NCMO (0.0 ≤ x ≤ 0.10). The samples were prepared by solid-state synthesis and characterized by various techniques like XRD, SEM, EDX, and ICPAES. The magnetization studies show that the Ni doping induces ferromagnetic phase at low temperatures. With the increase of Ni doping, though the CO phase is suppressed, the FMM phase also weakens which is different from the behaviour observed in Cr doped NCMO. The Ni doping induces insulator-metal transition and with increase of Ni doping, the metallic phase weakens. The magnetic anisotropy increases with increase of Ni doping as obtained from magnetization measurements and the EMR data also corroborates the same fact. The EMR studies in the paramagnetic phase indicate a CO phase for low Ni doping and the presence of short-range dynamical CO-OO correlations for higher Ni doping, which were not observed in magnetization studies. We observe two signals in the FM phase, which again can be attributed to the magnetic anisotropy. In chapter 5, we present EMR studies on nano-particles of Cr doped NCMO for x = 0.03. We have prepared nano-particles of three different sizes by the sol-get route. The samples were characterized by various techniques like XRD, SEM, EDX, and ICPAES. The particle sizes are 50, 100, 200 nm. We also compare the results of nano samples with the bulk samples. The ac susceptibility measurements show that the FM phase increases with the reduction of particle size. The EMR measurements show that the magnetic anisotropy decreases with decrease of particle size. The EMR linewidth in the paramagnetic phase increases with the decrease of particle size. The EMR intensity also increases with the reduction of particle size consitent with the magnetization results. The EMR results show that the reduction of particle size is one more way of inducing FM phase more effectively. Also the CO phase gets suppressed with the reduction of particle size. The two-signal feature is observed for all the particles. For nano-sized particles, the two signals appear in FM phase whereas in bulk sample they appeared well above TC. For 50 nm sized particles, the two signals appear well below 40 K. Thus we conclude that with decrease of particle size, the magnetic anisotropy decreases. The thesis concludes with a brief writeup summarizing the results and indicating possible future directions of research in the area.