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

We report anomalous magnetic reversal (MR)/negative magnetization (NM) state associated with the field induced switching of orbital moment ( μ L S m) of the Sm atom. This material shows an antiferromagnetic transition at Néel temperature ( T N ∼ 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 ( H E B) changes its sign across compensation temperatures for suitable field cooling (FC). We estimated a large FC inverse and conventional H E B of 8 and − 4.8 kOe at T = 130 K. Furthermore, the magnetic entropy change ( Δ S m) and adiabatic temperature change ( Δ T a d) calculated from the specific heat [ C p ( T , H )] measurements also show sign reversal at T ∗ ∗. These unusual behaviors are explained in terms of field induced switching of μ L S m, which is oppositely coupled to the spin moment of Sm ( μ S S m), Mn–Mn/Sm exchange interactions, and polarized conduction electron moment ( μ S C E P). Additionally, C p ( T , H ) exhibit Schottky anomaly around 3 K due to Zeeman splitting of Sm energy levels.