Structure, Magnetic, and Magnetocaloric Properties of Self-doped LaMnO3 Nanoparticles
Self-doped LaMnO3 has been known shown broad structure, magnetic and electric properties. Depend on the atomic stoichiometry, self-doped LaMnO3 shown large variation of ferromagnetic-paramagnetic (FM-PM) p...
Structure, Magnetic, and Magnetocaloric Properties of Self-doped LaMnO3 Nanoparticles
Self-doped LaMnO3 has been known shown broad structure, magnetic and electric properties. Depend on the atomic stoichiometry, self-doped LaMnO3 shown large variation of ferromagnetic-paramagnetic (FM-PM) phase transition temperature (the Curie temperature, TC). The atomic stoichiometry of LaMnO3 can be controlled by annealing temperature and the oxygen pressure during the annealing. At low annealing temperature and atmosphere pressure LaMnO3 strongly favors the off-stoichiometry phase. Meanwhile, at high annealing temperature and low oxygen pressure, LaMnO3 prefer to close to stoichiometry. The stoichiometry LaMnO3 well knows as A-type antiferromagnetic (AFM), on the other hand magnetic properties of off-stoichiometry phase could be a spin glass, FM or AFM insulator or a FM metal. In this work, we study the magnetic properties and magnetocaloric effect (MCE) of self-doped LaMnO3. The magnetic properties of self-doped LaMnO3 have been intensive studied, however, the MCE of has not been many reported. Furthermore, we have fabricated LaMnO3 nanoparticles (NPs) with different particle sizes, prepared by sol-gel method combined with heat treatment. Magnetization measurements versus temperature, M(T), indicate transition temperature (TC) close to room temperature and decreased gradually by increasing the particle size. This indicated the stoichiometry and crystal structure of LaMnO3 change by increases the particle size. Around TC, the maximum magnetic-entropy changes achieved from our work are much larger than those reported previously on LaMnO3 nanoparticle and comparable to single-crystal Gd. Based on the analyses of magnetic field dependencies of magnetic-entropy change and molecular field theory, we found that large entropy change in the self-doped LaMnO3 samples are due to magnetic phase transition change. Large magnetic entropy changes in large particle size associated with the first-order nature or the crossover behavior of the first- and second-order phase transition (FOPT and SOPT), while the small particle size exhibits the second-order nature.
Structure, Magnetic, and Magnetocaloric Properties of Self-doped LaMnO3 Nanoparticles
Self-doped LaMnO3 has been known shown broad structure, magnetic and electric properties. Depend on the atomic stoichiometry, self-doped LaMnO3 shown large variation of ferromagnetic-paramagnetic (FM-PM) phase transition temperature (the Curie temperature, TC). The atomic stoichiometry of LaMnO3 can be controlled by annealing temperature and the oxygen pressure during the annealing. At low annealing temperature and atmosphere pressure LaMnO3 strongly favors the off-stoichiometry phase. Meanwhile, at high annealing temperature and low oxygen pressure, LaMnO3 prefer to close to stoichiometry. The stoichiometry LaMnO3 well knows as A-type antiferromagnetic (AFM), on the other hand magnetic properties of off-stoichiometry phase could be a spin glass, FM or AFM insulator or a FM metal. In this work, we study the magnetic properties and magnetocaloric effect (MCE) of self-doped LaMnO3. The magnetic properties of self-doped LaMnO3 have been intensive studied, however, the MCE of has not been many reported. Furthermore, we have fabricated LaMnO3 nanoparticles (NPs) with different particle sizes, prepared by sol-gel method combined with heat treatment. Magnetization measurements versus temperature, M(T), indicate transition temperature (TC) close to room temperature and decreased gradually by increasing the particle size. This indicated the stoichiometry and crystal structure of LaMnO3 change by increases the particle size. Around TC, the maximum magnetic-entropy changes achieved from our work are much larger than those reported previously on LaMnO3 nanoparticle and comparable to single-crystal Gd. Based on the analyses of magnetic field dependencies of magnetic-entropy change and molecular field theory, we found that large entropy change in the self-doped LaMnO3 samples are due to magnetic phase transition change. Large magnetic entropy changes in large particle size associated with the first-order nature or the crossover behavior of the first- and second-order phase transition (FOPT and SOPT), while the small particle size exhibits the second-order nature.
학위논문 정보
저자
Pardi Sampe Tola
학위수여기관
Hankuk University of Foreign Studies. Graduate School
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