Influence of Fe and Cr doping on the structural and magnetic properties of ZnV₂O₄

In this paper, we report the modulation of structural and magnetic properties with Fe and Cr doping at the Zn and V sites in ZnV₂O₄. Undoped ZnV₂O₄ exhibits two anomalies in the M-T measurements which are assigned to a structural transition (T _S ~ 57 K) followed by a magnetic transition (T _N ~ 41 K). With the help of x-ray diffraction and energy dispersive x-ray analysis it is found that the prepared samples are single phase as well as stoichiometric. However, doping at both the cationic sites of ZnV₂O₄ leads to the disappearance of the structural transition and suppression of the long range magnetic ordering to a cusp like feature below 20 K and the cusps broaden with increasing magnetic field while the position of the cusps remain unaltered with increasing field strength. The obtained results indicate that Zn_1-x Fe _x V₂O₄ and Zn(V_1-t Cr _t )₂O₄ (x  =  t  =  0, 0.05, 0.1) systems are frustrated cubic normal spinel systems. Moreover, such field independent behavior of cusp positions hints towards the antiferromagnetic ground state at low temperature instead of a spin glass phase. To elucidate this fact, dc aging (magnetic relaxation) and memory effects have been investigated in zero field cooled (ZFC) and field cooled (FC) protocol for the 10% doped samples, which exhibit aging and memory effect. Our study provides an explicit evidence of spin glass like state instead of low temperature antiferromagnetic ground state in the doped compounds.