Magnetic irreversibility, spin-wave excitations and magnetocaloric effect in nanocrystalline Gadolinium

A detailed study of irreversibility in magnetization,spin-wave excitations, approach-to-saturation and magnetocaloric effect in nanocrystalline Gd revealed the following. Intra-grain and the interfacial (grain boundaries) magnetic anisotropies play a decisive role in causing irreversibility in magnetization and in considerably slowing down the approach to saturation. Compared to that in Gd single crystal, the spin wave stiffness is essentially unaltered but the field-induced change in magnetic entropy (magnetocaloric effect) is roughly 1.5 times smaller because, in the presence of large interfacial magnetic anisotropy, even fields as intense as 120 kOe do not suffice to remove the misalignment of spins completely.