Coexistence of spin glass and superparamagnetism with ferrimagnetic order in polycrystalline spinel Co0.2Zn0.8Fe1.95Ho0.05O4

We discuss our investigation of DC magnetization, as a function of time, temperature and magnetic field, and explore some distinct magnetic behaviour in the polycrystalline spinel Co0.2Zr0.8Fe1.95Ho0.05O4. The system is essentially to be a ferrimagnet and the ferrimagnetic order (spontaneous magnetization) is identified using Arrot plot of M(H) data. Application of some scaling laws have shown the coexistence of spin glass (SG) and superparamagnetism (SPM) with ferrimagnetic order (FIMO) at low and high temperature, respectively, in the system. The coexistence of SG and SPM with FIMO shows paramagnetic to ferrimagnetic state at T-C approximate to 225 K and ferrimagnetic to cluster spin glass state below T-m approximate to 120 K. The non-linear increase, without hysteresis, of AI(H) data above TC indicates the existence of short range interacting clusters in the paramagnetic state. In addition, the anisotropy effect of Ho3+ has shown some interesting magnetic features, such as, spin glass of Ising nature and an usual maximum in the thermoremanent magnetization about 180 K. (c) 2005 Elsevier B.V. All rights reserved.