Study of magnetic and thermal properties of SmCrO3 polycrystallites

Abstract

In the present work, we have studied the magnetic and thermal properties of sol gel derived samarium chromite (SCO) polycrystallites. The magnetic measurements of SCO polycrystallites show a characteristic antiferromagnetic transition T_N ∼ 190 K and spin reorientation temperature T_SR ∼ 33 K, which is in the region of interest to study a possible magnetocaloric effect (MCE). The isothermal magnetic entropy change (ΔS_M) is estimated by an indirect method from the isothermal magnetization curves measured in this temperature range. The SCO polycrystallites possesses both inverse (positive) and normal (negative) MCE at and above around the spin reorientation transition (T_SR) with −ΔS^max_M values of ∼−24 × 10⁻² & 13 × 10⁻² J kg⁻¹ K⁻¹, respectively. The SCO also shows another normal (negative) MCE peak around its Néel transition (T_N) with −ΔS^max_M ∼ 11 × 10⁻² J kg⁻¹ K⁻¹. The presence of two successive MCE peaks in SCO in the temperature range of 3–50 K, leads to an ∼47 K operating temperature window with one thermodynamic cycle. In addition, the low temperature heat capacity (C_P) measurements of SCO polycrystallites reveal a λ-shaped peak at T_N which is associated with a conventional second-order, paramagnetic to antiferromagnetic (AFM), phase transition. The temperature and magnetic field dependence of the specific heat capacity was studied and analyzed to estimate the adiabatic temperature change (ΔT_ad). In addition the C_P vs. T curve in SCO also shows a weak anomaly around the ∼T_SR along with a Schottky anomaly below 10 K.