The effect of Fe-doping in magnetic properties of frustrated spinel CoAl2O4

Abstract

In this work, we study the effect of Fe-doping in the magnetic properties of CoAl 2 O 4 , which presents a very high level of frustration. Samples are synthesized via solid state reaction by mixing stoichiometric amounts of CoO, Fe 2 O 3 and Al 2 O 3 starting oxides. The analysis of X-ray data show that our samples are single phase with cubic symmetry and space group f d − 3 m . A decrease of lattice parameter as a function of iron concentration is also inferred from the X-ray data. As compared with the pure sample, temperature dependence of magnetization of doped samples show an additional phase transition at high temperature. The enhancement of thermal hysteresis effect and the increasing of the Curie-Weiss temperatures with the Fe-doping can be an indicative of magnetic phase competition leading to a frustrated ground state. Indeed, the unsaturated state of the M v s H loops measured at T = 2 K is consistent with the strong frustration phenomenon. Finally, we argue that the displace of the low temperature peak, which is associated with the freezing temperature in the pure sample, into high temperature region as a function of Fe-doping can be relieving the frustration effect due the next-nearest-neighbor antiferromagnetic interaction J 2 . • Increase of lattice parameters a function of iron concentration. • Fe-doping the highly frustrated material CoAl 2 O 4 . • Magnetic phase competition in low temperature region.