Singha, A.D.; Seehra, M.S.; Skoulatos, M.; Sarkar, T.; Pramanik, P.; Chowdhury, S.; Hoesch, M.; Reehuis, M.; Többens, D.M.; Raghu, A.; Kaushik, S.D.; Thota, S.: Anisotropy driven spin-reorientation, and two-step magnetic ordering in cubic semiconducting spinel Cr0.1Mn0.9Fe0.2Co1.8O4. Journal of Physics: Condensed Matter 37 (2025), p. 225802/1-14
10.1088/1361-648x/add63d
Abstract:
The nature of magnetism in the cubic spinel is reported based on systematic investigations by means of magnetization (M), ac susceptibility (χ) and heat capacity (Cp) measurements, as well as by neutron diffraction. Structural characterization of the sample was done using x-ray absorption spectroscopy, neutron and synchrotron diffraction. The M vs. T variation in different magnetic fields indicate ferrimagnetic ordering below TC = 230 K, followed by a magnetic field and anisotropy induced spin reorientation at TSR ~ 150 K. With increasing T starting from 2 K, the coercivity and anisotropy field HK decrease and become negligible for T > TSR. A model to explain the HC vs. T data shows that TSR is due to reorientation of M along H when H > HK. The CP vs. T data shows a weak lambda-type anomaly at TC with changes in magnetic entropy smaller than those observed below TSR suggesting that long-range magnetic ordering is completed below TSR. For TSR < T < TC, the presence of weakly interacting magnetic clusters having weak short-range interactions is evident based on analysis of magnetization and ac susceptibilities. Exchange constants (JAA/ = 7.9 K, JAB/kB = 22.6 K and JBB/kB = –5.3 K) are determined from the temperature dependence of paramagnetic susceptibility for T > TC . This analysis also shows the low-spin S = 0 state of Co3+ ions on the B sites which along with negligible HK for TSR < T< TC produces weakly interacting magnetic clusters in this magnetic semiconductor with bandgap ~0.57 eV.