Colossal magnetoresistance in spinel type Zn_(1-x)Ni_(x)Fe_(2)O_(4)

摘要

Spinel-type ferrites are widely used in practical applications. A fascinating property of Zn-Ni ferrites which reveals a direction for application is reported. A large negative magnetoresistance effect has been observed in ZnFe_(2)O_(4) and Ni substituted Zn_(1-x)Ni_(x)Fe_(2)O_(4) ferrites of spinel structure. These materials are either ferrimagnetic or paramagnetic at room temperature and a spin (cluster) glass transition was found for some compositions at low temperatures. The magnetoresistance is either parabolic or linear with respect to applied field up to 9 T depending on the compositions and temperatures. It was found that the magnetoresistance effect increases as the Ni content increases in Zn_(1-x)Ni_(x)Fe_(2)O_(4) up to x=0.2 and then again decreases and finally become negligible for x=1.0, i.e., NiFe_(2)O_(4). This magnetoresistance effect can be explained with the help of spin-dependent scattering and the Yafet-Kittel angle of the Ni-substituted Zn-Ni ferrites.