The multiferroic compound, Co(Cr0.95Fe0.05)2O4, displays reversal in the orientation of magnetic moments along with negative magnetization due to an underlying magnetic compensation phenomenon, which was earlier not noticed in the parent compound of CoCr2O4. This is one of the compounds with spinel structure where the exchange bias field changes sign across the compensation temperature and therefore has the potential attribute to get tuned in a preselected manner. In this letter, we shall elucidate the sign reversal of the exchange bias on the premise of the sign reversal of the magnetic moments, which is confirmed by the specific heat measurements.
A small amount of Fe (5% and 7.5%) substitution in the Cr-site of the multiferroic compound CoCr2O4 leads to a magnetization reversal. In these compounds, we report a sign change in the exchange bias across the compensation temperature, accompanied by a non-monotonic change in the local moments across the compensation temperature. Such non-monotonic change in the magnetic moments is triggered by a similar change in the lattice structure. We relate here the sign change of exchange bias with that of the crystalline energy of the lattice and the Zeeman energy term arising from the anti-site disorder.
We report the magnetic structures of an Fe substituted cobalt chromite system, Co(Cr1−xFex)2O4 (x = 0.05 and 0.075), determined from the analysis of temperature dependent neutron diffraction measurements.
We present the evolution of novel phenomena of magnetic compensation effect, exchange bias (EB) effect and the field induced anomalies in '[Formula: see text]' substituted multiferroic compound [Formula: see text]. A few percent of '[Formula: see text]' substitution for '[Formula: see text]' in [Formula: see text] results in the reversal of field cooled magnetization under low applied fields below compensation temperature T . Further, increase in the field leads to the spin reorientation transition (T ). Signature of EB in a narrow temperature window in the vicinity of T and its sign change across T is observed. Magnitude of EB depends on the amount of compensation and rigidity of the spin reorientation. We also notice the appearance of positive EB below the lock-in transition (T). Presence of unidirectional anisotropy developed in the commensurate spin-spiral below T could be responsible for the appearance of EB below T.
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