Magnetism and heat capacity of Dy<SUB>5</SUB>Si<SUB>2</SUB>Ge<SUB>2</SUB>

Magnetic and thermal properties of the compound Dy5Si2Ge2 (orthorhombic, Sm5Ge4-type) have been studied. This compound orders antiferromagnetically at 56K (TN), with a positive paramagnetic Curie temperature (&#952;P) indicating the presence of competing magnetic interactions. Zero-field-cooled and field-cooled magnetization data obtained in a low field of 5 mT show irreversibility that starts above TN, giving rise to a deviation from the paramagnetic Curie-Weiss behavior, in the temperature range of 56-100K. Magnetization vs field (M vs H) isotherms below 40 K display a metamagnetic transition (MMT) and at 2K, a sharp, martensiticlike, step in magnetization at a critical field of ~2.9 T. Heat capacity measurements on this compound in zero applied field exhibit a peak at TN which gets subsequently suppressed on application of magnetic fields of 5 T and 9 T. The MMT is found to have a dominant role in the associated magnetocaloric effect. The isothermal entropy change (&#916;Sm) and the adiabatic temperature change (&#916;Tad) are found to be ~8 J/mol K and ~6 K, respectively, for 9 T field change, in the vicinity of TN. The reversible metamagnetic behavior is envisaged to arise from strong magnetocrystalline anisotropy and/or due to a possible field-induced structural transition as observed in the isostructural Gd5Ge4 compound