Low-temperature anomalous magnetic behavior of Co2TiO4 and Co2SnO4

Abstract

We report the low-temperature anomalous magnetic behavior of ferrimagnetic spinels cobalt orthotitanate (Co2TiO4), which exhibits magnetic compensation behavior across 31.74 K, and cobalt orthostannate (Co2SnO4) exhibiting two sequential magnetic transitions, namely (i) ferrimagnetic to paramagnetic transition with Néel temperature TN ∼ 41 K and reentrant spin-glass behavior with glass transition temperature TSG ∼ 39 K. The Arrott plot (H/M versus M2) criterion has been used to extricate the order of sequential magnetic transitions occurring below TN. Negative slopes of the Arrott plots below 32 K, metamagnetic-like character of the M-H isotherms, anomalies in the specific-heat (CP T−1 versus T) below 15 K, and a zero-crossover of isothermal magnetic-entropy-change (ΔS) signify the presence of pseudo first-order discontinuous magnetic phase transition in the low-temperature regime 5 K ≤ T ≤ 32 K. The dc- and ac-susceptibilities of both Co2TiO4 and Co2SnO4 are interpreted in terms of frozen-spin-clusters, which are responsible for very large magnitudes of the coercivity HC ∼ 20 kOe and bipolar-exchange bias HEB ∼ −20 kOe observed below 10 K.