Heat capacity and thermal expansion of gadolinium tetraboride at low temperatures

Abstract

Temperature dependences of heat capacity and lattice parameters of gadolinium tetraboride (GdB4) at the temperatures of 2–300 K have been studied experimentally. In the course of the experiment, the anomalies of these properties caused by the processes of transition into the antiferromagnetic state at TN = 41.87 K were revealed. Temperature changes of electronic and lattice, the magnetic contribution to GdB4 heat capacity, as well as the Schottky contribution were singled out and analyzed. Residual entropy of the Gd3+ magnetic subsystem caused by frustration was found to be Rln3.2. Temperature variations of linear and volumetric thermal expansion coefficients were calculated. It was established that processes of magnetic ordering in GdB4 give rise to a negative spontaneous magnetostriction and are not accompanied by the distortion of the crystalline lattice.