Magnetization, ESR and large magnetocaloric effect in zigzag chain SrGd2O4

We performed the magnetization and electron spin resonance (ESR) measurements in the zigzag chain antiferromagnet SrGd2O4. First, the temperature-dependent ESR spectra suggest the presence of spin-spin correlations well above the ordering temperature due to geometric frustration. Second, the ESR data reveal the field-induced magnetic transition from an ordered state to a paramagnetic state, in accordance with the magnetization data. Third, the magnetization process exhibits a large magnetocaloric effect, which is associated with the alignment of paramagnetic spins along the direction of magnetic field. The maximum magnetic entropy change (-Delta S-M) near 3K and refrigerant capacity (RCP) are 27 J.Kg(-1).K-1 and 325 J.Kg(-1), respectively, for a field change of 0-7 T. With negligible thermal and field hysteresis, SrGd2O4 can be considered as a cryogenic refrigerant material.