Abstract. 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.
We report on how nanocrystal size affects the critical behaviour of the rare-earth metal Gd near the ferromagnetic-to-paramagnetic phase transition. The asymptotic critical behaviour of the coarse-grained polycrystalline sample (with an average crystallite size of L≅100 μm) is that of a (pure) uniaxial dipolar ferromagnet, as is the case with single crystal Gd, albeit the width of the asymptotic critical region (ACR) is reduced. As the grain size approaches ∼30 nm, the ACR is so narrow that it could not be accessed in the present experiments. Inaccessibly narrow ACR for L ∼ 30 nm and continuous increase in the width of the ACR as L decreases from 16 to 9.5 nm basically reflect a crossover to the random uniaxial dipolar fixed point caused by the quenched random exchange disorder prevalent at the internal interfaces (grain boundaries).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.