Anomalous Magnetic Properties in LaFe11.5Al1.5
We account the magnetic relaxation, dc magnetization, heat capacity, and the studies of X-ray powder diffraction for melt-spun LaFe11.5Al1.5 compound executed in a range of temperatures from 5K to 300K. We have found three magnetic transitions (at temperatures T1, T2, and Tord) in this compound in the zero-field cooled (ZFC) mode, and two magnetic transitions (at T2 and Tord) in field-cooled cooling/warming (FCC/FCW) mode. The ferromagnetic transition (FM) at temperature T2 enunciating a hysteresis alludes to a magnetic transition of first-order (FOT) at lower temperatures. The magnetization study reveals that meta-stable states exist in the low-temperature antiferromagnetically ordered state. A partially reversible behavior is also observed in the 120-140 K temperature range. The heat capacity data exhibits that the magnetic state of this compound is clearly different from that of the spin-glasses. The magnetocaloric properties of the compound are determined in the form of the isothermal magnetic entropy change (∆SM) and the adiabatic temperature change (∆Tad) and observed the utmost value of ∆SM and ∆Tad for a field variation of 25 kOe to be 3.1 J/kg K and 1.12 K respectively. The RCP is ascertained to be 216 J/kg for an enforced field of 25 kOe.