ИСТИНА

We report on static and dynamic magnetic properties of GdFeTeO6 with super- structure of the rosiaite type. Both the magnetic susceptibility and the specific heat of GdFeTeO6 unambiguously confirm the onset of long range ordering at TN = 2.4 K, which is suppressed quickly in applied external magnetic fields. This suppression is accompanying by appearance of Gd-related Shottky-type anomaly on the Cp(T). Based on the thermodynamic studies, the magnetic B-T phase diagram was constructed. Spin dynamic properties investigated by electron spin resonance (ESR) corroborate static magnetic ones and indicate rather 2D character of magnetic interactions. ESR spectra in the paramagnetic phase demonstrate a single broad line, which can be assigned to averaged response from gadolinium and iron subsystems and characterized by the isotropic effective g-factor g = 2.00 ± 0.1, typical for S-type ions Gd3+ (S = 7/2) and Fe3+ (S = 5/2) in octahedral oxygen coordination. Broadening of the ESR line as temperature decreases is typical for AFM compounds and the critical exponent corresponds to rather 2D character of AFM magnetic correlations. In accordance with our magnetocaloric data, for a magnetic field change of 9 T, the maximum values of –ΔSM(T) = 35.3 J/kg K, ∆Tad = 27 K, rela- tive cooling power (RCP) and refrigerant capacity (RC), are 580 J/kg and 465 J/kg, respectively. So, all MCE parameters are remarkably large in GdFeTeO6, that makes this system interesting for potential application as low-temperature magnetic refrigerator (MR), for example for design of hydrogen liquefier MR.