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We report high-sensitivity experiments utilizing the magneto-optic Kerr effect which probe for ferromagnetism in ultrathin epitaxial films of Pd and V on Ag(100) substrates. Our experiments fail to detect unambiguous manifestations of ferromagnetism in these two thin-film systems.Recent theoretical' and experimental efforts have addressed an interesting issue: the possible existence of ferromagnetism in thin-film structures of metals that are not ferromagnetic in thier naturally occurring bulk form. Two elements V and Pd have been singled out as particularly attractive candidates for exhibiting ferromagnetism induced by stabilizing a two-dimensional epitaxial film having an expanded lattice constant. Atomic V has a large magnetic moment resulting from spin alignment governed by Hund's rule (3@~), and although atomic Pd has no magnetic moment (its ground state is 4d ' Ss ) it is isoelectronic with Ni which is ferromagnetic in its metallic state. Formation of the conduction bands in V and Pd is accompanied by a partial destruction of the atomic character of the d states and other valence levels (hybridization and quenching of orbital momentum) but in both instances the result is a metal which exhibits strong paramagnetic susceptibility.The ability to stabilize thin epitaxial layers having lower symmetry, reduced atomic coordination, and significantly increased neighbor distances compared with the bulk materials offers the possibility of inducing novel magnetic behavior in thin-film structures.Indeed, firstprinciples calculations tailored to the structure of surface layers on bulk crystals and epitaxial thin-film structures have predicted a rich variety of new magnetic phenomena. ' 4 Experiments reported in the present paper address the possibility of induced magnetism in epitaxial films of V and Pd on Ag (100) surfaces. An appreciable amount of experimental and theoretical work on these two systems has already appeared. The first computational studies of V on Ag(100) predicted enhanced magnetic moments and ferromagnetic ordering. ' Corresponding calculations including spin-orbit effects predicted ferromagnetism in free-standing V monolayers (having the Ag lattice constant). In these calculations, the crystalline anisotropy favors spin alignment perpendicular to the film plane, but the shape anisotropy is dominant and forces the spin to lie in the 61m plane. Subsequent calculations, however, suggest that the ground state of V on Ag (100) is an antiferromagnetic c(2X2) state. Four experiments have explored the magnetic properties of V grown on Ag(100). Electron-capturespectroscopy (ECS) experiments appear to indicate that a p(1X1) monolayer of V on Ag(100) is ferromagnetic, with in-plane magnetization and a transition temperature of 475 K. The temperature dependence of the magnetization inferred from ECS studies of a five-layer V film on Ag(100) yielded critical behavior in good agreement with the two-dimensional Ising model (experimentally determined exponent P=O. 128+0.01). More recently, Moodera and Meservey have ...

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