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. $\mathrm{Pd}-G\left(1\right)\mathrm{}$ is an itinerant spin system with an antiferromagnetic ordered phase below $T_N(=3.8\mathrm{}\mathrm{K}).\mathrm{}$ No spin-glass-like behavior occurs around $T_N.$ $\mathrm{P}\mathrm{d}-G\left(2\right)\mathrm{}$ is a quasi-two-dimensional XY-like ferromagnet with very weak antiferromagnetic interplanar interaction. It undergoes two magnetic phase transitions at $T_{\mathrm{cu}}(=14.2\mathrm{}\pm 0.2\mathrm{K})$ and $T_{\mathrm{cl}}(=11\mathrm{}\mathrm{K}).\mathrm{}$ Between $T_{\mathrm{cu}}$ and $T_{\mathrm{cl}},$ a two-dimensional ferromagnetic spin order is established within nanoparticles in the Pd layers. Below $T_{\mathrm{cl}}$ there appears a three-dimensional antiferromagnetic ordered phase.