巨磁电阻材料A_(0.05)Co_(0.95)Cr_2S_4(A=Zn、Ni、Cd、Fe)的输运行为及磁性能研究

Transport Behavior and Magnetism of Colossal Magnetoresistance Materials A_(0.05)Co_(0.95)Cr_2S_4(A=Zn、Ni、Cd、Fe)

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_(0.05)Co_(0.95)Cr_2S_4(A=Zn、Ni、Cd、Fe)样品,研究磁性和非磁性元素掺杂对Co Cr2S4晶体结构和磁性能的影响。XRD检测表明,掺杂的A_(0.05)Co_(0.95)Cr_2S_4(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_(0.05)Co_(0.95)Cr_2S_4(A=Zn、Ni、Cd、Fe)均具有巨磁电阻效应。掺杂削弱了铁磁相互作用,导致A_(0.05)Co_(0.95)Cr_2S_4(A=Zn、Ni、Cd、Fe)的居里温度TC降低。在0.01 T下,A_(0.05)Co_(0.95)Cr_2S_4(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_(0.05)Co_(0.95)Cr_2S_4(A=Zn、Ni、Cd、Fe)呈现典型的亚铁磁性磁滞回线,其中Zn0.05Co0.95Cr2S4的矫顽场最大。

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 A0.05Co0.95Cr2S4（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 Co Cr2S4 after doping were studied.XRD measurement shows that the doped A0.05Co0.95Cr2S4（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 TC of A0.05Co0.95Cr2S4（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 Zn0.05Co0.95Cr2S4 shows the largest value of coercivity.