Magnetic properties of palladium-graphite multilayers

Dc magnetization and ac magnetic susceptibility of Pd graphite based on natural graphite have been measured using a superconducting quantum interference device magnetometer. In Pd-G, Pd multilayers are sandwiched between adjacent graphite layers. This sandwich structure is periodically stacked along the c axis. Pd layers are formed of Pd nanoparticles in the form of either a one-dimensional chain or two-dimensional platelets. There are two kinds of magnetic behavior depending on sample. Pd-G(1) is an itinerant spin system with an antiferromagnetic ordered phase below T-N(= 3.8 K). No spin-glass-like behavior occurs around T-N. Pd-G(2) is a quasi-two-dimensional XY-like ferromagnet with very weak antiferromagnetic interplanar interaction. It undergoes two magnetic phase transitions at T-cu(= 14.2+/-0.2 K) and T-cl(= 11 K). Between T-cu and T-cl, a two-dimensional ferromagnetic spin order is established within nanoparticles in the Pd layers. Below T-cl there appears a three-dimensional antiferromagnetic ordered phase.