DC-magnetisation studies in the La_1-xSr_xCoO₃ (x ≤ 0.4) system

Abstract

The magnetic field and temperature dependence of DC-magnetisation in polycrystalline samples of La_1-xSr_xCoO₃ (x≤0.4) (LSCO) perovskite system is being studied using a SQUID magnetometer. We find that for Sr-concentration, x≥0.2, a sharp increase in magnetisation is observed in the temperature regime of 200-230 K. Strong thermomagnetic irreversibility (i.e. M_ZFC≠M_FC) in the entire investigated composition regime is found in this system. Furthermore, we observed a mild hysteresis and small coercivity in the M-H scans performed at various temperatures in samples with x≥0.2. The observed magnetic behaviour in these samples clearly indicates that for x≥0.2, LSCO is a soft ferromagnet. We interpret that the observed thermomagnetic irreversibility arises from large magnetocrystalline anisotropy, which at low external applied magnetic fields effectively pins the ferromagnetic (FM) domains.