巨磁电阻材料A0.05Co0.95Cr2S4(A=Zn、Ni、Cd、Fe)的输运行为及磁性能研究

过渡金属尖晶石型硫化物具有包括超巨磁电阻(CMR)效应在内的多种物理性能, 其CMR效应机理的研究对开发巨磁电阻材料有重要价值。目前, 铬基硫族尖晶石的CMR效应尚未深入研究。本论文通过固相反应法制备A_0.05Co_0.95Cr₂S₄(A=Zn、Ni、Cd、Fe)样品, 研究磁性和非磁性元素掺杂对CoCr₂S₄晶体结构和磁性能的影响。XRD检测表明, 掺杂的A_0.05Co_0.95Cr₂S₄(A=Zn、Ni、Cd、Fe)均呈现纯的尖晶石结构, 掺杂导致的晶胞参数变化与掺杂元素的离子半径成比例。磁电阻测定表明A_0.05Co_0.95Cr₂S₄(A=Zn、Ni、Fe)均具有巨磁电阻效应。掺杂削弱了铁磁相互作用, 导致A_0.05Co_0.95Cr₂S₄(A=Zn、Ni、Cd、Fe)的居里温度T_C降低。在0.01 T下, A_0.05Co_0.95Cr₂S₄(A=Zn、Ni、Cd、Fe)的零场冷却(ZFC)和加场冷却(FC)曲线均呈现磁性不可逆现象。A_0.05Co_0.95Cr₂S₄(A=Zn、Ni、Cd、Fe)呈现典型的亚铁磁性磁滞回线, 其中Zn_0.05Co_0.95Cr₂S₄的矫顽场最大。

Transport Behavior and Magnetism of Colossal Magnetoresistance Materials A0.05Co0.95Cr2S4 (A=Zn,Ni, Cd,Fe)

Spinel-type transition metal sulfides possess various super physical properties including colossal magnetoresistance (CMR). The research of the mechanism of the CMR effect is of great value for the development of the CMR sulfide materials, whereas the CMR effect of the spinel chrome-based sulfides is unclear up till now. The A_0.05Co_0.95Cr₂S₄ (A=Zn, Ni, Cd, Fe) samples were prepared by solid-state reaction method. Their effects of magnetic and non-magnetic metal elements on crystal structure and magnetic properties of CoCr₂S₄ after doping were studied. XRD measurement shows that the doped A_0.05Co_0.95Cr₂S₄ (A=Zn, Ni, Cd, Fe) samples exhibit pure spinel structure, in which their crystal cell parameters increase proportional to the ionic radius of the doping elements. Magnetoresistance measurement shows that all the samples exhibit giant magnetoresistance effect. Doping weakens the ferromagnetic interaction, which leads to the decrease of T_C of A_0.05Co_0.95Cr₂S₄ (A=Zn, Ni, Cd, Fe). In the low field of 0.01 T, the curves of the zero-field cooling (ZFC) and field cooling (FC) exhibit magnetic irreversible phenomena. All the samples exhibit typical ferrimagnetic hysteresis loops, among which Zn_0.05Co_0.95Cr₂S₄ shows the largest value of coercivity.