Magnetic properties of F- and P-type icosahedral quasicrystals of Al - Pd - Mn

The magnetization of F- and P-type icosahedral Al - Pd - Mn was studied in the temperature region between 2 and 870 K in a magnetic field below 80 kOe. F-type icosahedral phase samples obtained by quenching from 1075 K were transformed to the low-temperature-phase form during the magnetic measurement above 600 K. The low-temperature phase is a P-type phase; this phase is characterized by a superlattice ordering. The samples showed Curie - Weiss paramagnetism and increasing susceptibility with increasing temperature at high temperatures. The increasing susceptibility is accounted for by a temperature dependence of the Pauli paramagnetism arising from a pseudogap at in the electronic density of states. The increase in the P phase was larger than that in the F phase, which indicates an enhanced pseudogap in the P phase. This is consistent with a structural transformation to a more stable P phase caused by the in situ heat treatment. The Curie - Weiss susceptibility decreased after the structural transformation from F- to P-type structure had occurred. A reduction by about one half in the number of magnetic Mn atoms in the transformation is inferred. The temperature dependence of the susceptibility deviates from the Curie - Weiss law below 30 K, which is similar to what was found in a previous report by Chernikov and co-workers, but the deviation is much smaller.