Magnetic properties and magnetocaloric effect in [formula omitted] compounds

Magnetic properties and magnetocaloric effect of compounds [formula omitted] [formula omitted] are investigated experimentally. All the compounds crystallize in the hexagonal [formula omitted]-type structure and show a sharp drop in the magnetization around their respective magnetic ordering temperature, which is 201 K [formula omitted], 147 K [formula omitted], and 98 K [formula omitted], respectively. Either thermal or magnetic hysteresis around the phase transition is not observed, suggesting a second order phase transition nature. The magnetic entropy change [formula omitted] calculated from the Maxwell relation using the collected magnetization data is 10.6 [formula omitted], 7.3 [formula omitted], and [formula omitted] [formula omitted], respectively. The shape of the [formula omitted] curve has a good symmetry below and above the magnetic ordering temperature, and the value of the magnetic entropy change increases monotonously with increasing field change. The calorimetric technique has also been used for [formula omitted] to check the credibility of the magnetic method.