Magnetic Properties In The Ceramic Of La_0.4Ca_0.6MnO₃Materials Doped With Cr

Perovskite manganeses are the typical materials of colossal magnetoresistance (CMR), the strong coupling among the charge,spin,orbit, lattice degree of freedom gives rise to complex electronic and magnetic properties appear in doped manganites, which attract people’s interest in this area. La0.4Ca0.6MnO3is the typical materials of charge-ordering manganite, and studies have shown that external magnetic field and B-site doping can strongly affect the magnetic properties of charge-ordering manganite. In this paper, charge-ordering manganese La0.4Ca0.6Mn1-xCrxO3polycrystalline ceramic samples were studies on both the charge-ordered state and magnetic transition in the steady-state magnetic fields and pulsed magnetic field. The main contents are shown as followed:First, we introduce the basic properties of perovskite manganite briefly, discuss the concept and the stability influence of charge-ordered state. Based on these theories, we propose the research significance of this article.Secondly, we use standard solid-state method to synthesize Lao.4Ca0.6Mn1-xCrxO3polycrystalline ceramic samples. And introduce the testing techniques which used in this article.Thirdly, study on the magnetic properties of Lao.4Cao.6Mn1-xCrxO3system. The M-T curve indicate that charge—ordered antiferromagnetic exists in undoped Lao.4Cao.6Mn03sample. With the introduction of Cr3+ions, charge-ordering state can be destroyed, and the antiferromagnetic has been weakened, cause the transition from AFM to FM, confirm the coupling between charge-ordered and magnetic-ordered. From M-Hcurve we can see that with the concentration of Cr doping increases, the magnetization of LCMO samples increase. When.x＝0.2, the magnetization decreased, indicating that antiferromagnetic superexchange between Cr3+—Cr3+had great influence on magnetic properties of LCMO system. Description that the substitution of Cr3+for Mn3+can strongly affect the magnetic transition of charge-ordering manganite. Lastly, give a brief introduction of pulsed magnetic field and study the magnetic properties of Lao.4Cao.6Mn1-xCrxO3system in pulsed magnetic field. Undoped Lao.4Cao.6Mn03samples need a very strong external magnetic field to destroy the charge-ordered and induced AFM-FM transition, which confirmed the stability of charge-ordered state. With the doping concentration increase, charge-ordered state has been destroyed and the coupling of antiferromagnetic has been weekend, with lower magnetic field that can induce AFM-FM transition. When the doping concentration increase to0.2, the transition feature in M-H curve vanish, which point to the disappearance of the AFM ordering and exhibit FM ordering.