Multiple magnetization reversal and field induced orbital moment switching in intermetallic SmMnSi compound

Abstract

We report anomalous magnetic reversal (MR)/negative magnetization (NM) state associated with the field induced switching of orbital moment (μLSm) of the Sm atom. This material shows an antiferromagnetic transition at Néel temperature (TN∼240 K) followed by a NM state in between compensation temperatures (T∗ and T∗∗). The MR/NM state vanishes above 12.5 kOe, while T∗ and T∗∗ follow opposite magnetic field dependency in field cooled cooling (FCC) magnetization. In the high field (H>20 kOe), the thermo-magnetization [M(T)] curve produces a mirror like inversion in magnetization within (T∗−T∗∗) with respect to its low field FCC counterpart. Within the NM region, the exchange bias field (HEB) changes its sign across compensation temperatures for suitable field cooling (FC). We estimated a large FC inverse and conventional HEB of 8 and −4.8 kOe at T=130 K. Furthermore, the magnetic entropy change (ΔSm) and adiabatic temperature change (ΔTad) calculated from the specific heat [Cp(T,H)] measurements also show sign reversal at T∗∗. These unusual behaviors are explained in terms of field induced switching of μLSm, which is oppositely coupled to the spin moment of Sm (μSSm), Mn–Mn/Sm exchange interactions, and polarized conduction electron moment (μSCEP). Additionally, Cp(T,H) exhibit Schottky anomaly around 3 K due to Zeeman splitting of Sm energy levels.