Epitaxially induced anisotropy in thin films of Laves phase compounds

Thin films of $\rm DyFe_2$ and $\rm ErFe_2$ have been epitaxially grown along the [110] direction. At 4.2 K, the easy magnetization axis in the films, determined by Mössbauer spectroscopy, is the same as in bulk compounds (i.e. $\langle100\rangle$ for $\rm DyFe_2$ and $\langle111\rangle$ for ${\rm ErFe_2}$). At 300 K, the magnetic moments, which remain in the same direction as at 4.2 K in bulk compounds, rotate towards $\langle110\rangle$ directions in thin films: they are close to the in-plane $[1\overline10]$ direction in $\rm DyFe_2$ films, and close to the perpendicular-to-the-plane [110] direction in $\rm ErFe_2$ films. These modifications of the magnetic anisotropy are related to the epitaxial strains, and to the sign and the relative importance of the anisotropy and magnetoelastic constants of the compound

Engineering coercivity in YFe2 dominated DyFe2/YFe2 superlattice by patterning

Single crystal 400 nm thick Laves phase [20 Å DyFe2/80 Å YFe2]40 superlattice have been grown by MBE with a (110) growth direction. VSM measurements performed at room temperature with an applied field range of ±1.2×105 Oe, directed along the [001] direction, reveal a unique single-phase-liked ferrimagnetic behavior. A dominant exchange spring behavior is revealed by MOKE measurement along the [–110] direction. Furthermore, for striped arrays patterned along the [001] direction with height-to-width ratio of 0.05, a shape anisotropy of the order of 104 erg/cm3 is induced, resulting into a pronounced change of coercivity due to the comparable magnitude with intrinsic anisotropies. The results demonstrate the feasibility of engineering both single-phase-liked and exchange-spring magnet behavior in Laves phase epitaxial hard/soft superlattices by patterning

Giant magnetoresistance by exchange springs in DyFe2/YFe2 superlattices

Magnetization and magnetoresistance measurements are reported for antiferromagnetically coupled DyFe2/YFe2 multilayers in fields up to 23 T. It is demonstrated that the formation of short exchange springs ( ~20 Å) in the magnetically soft YFe2 layers results in a giant magnetoresistance as high as 32% in the spring region. It is shown that both the magnitude of the effect and its dependence on magnetic field are in good agreement with the theory of Levy and Zhang for domain wall induced giant magnetoresistance