Magnetic force microscopy characterization of unusual magnetic coupling in an extraordinarily responsive magnetic material

Summary for only given. Gd/sub 5/(Si/sub 2/Ge/sub 2/) and compounds of similar composition (near 2Si-2Ge) exhibit large magneto-responsive properties including a colossal magnetocaloric effect, giant magnetostriction, and giant magnetoresistance near a structural-magnetic phase transition close to room temperature. Magnetic force microscopy (MFM) and vibrating sample magnetometry (VSM) measurements on single crystals indicate that a large fraction of the magnetization vector is along a direction perpendicular to the atomic "slabs", the b axis of the orthorhombic magnetic phase. Therefore, it appears that Gd/sub 5/(Si/sub x/Ge/sub 1-x/)/sub 4/ should be modeled in the same way as other multilayers and superlattices of rare-earth (R) metals and one or more nonmagnetic constituents that exhibit long range magnetic structures with order across the nonmagnetic layers. Many of the important phenomena of the Gd compounds, including a transition that can be induced by magnetic field, could be explained by the interaction of localized magnetic moments across the covalent bonding between "slabs", adapting models already offered for other similar materials.