High‐Temperature Heat Capacity of Ferromagnets Having 1st‐ and 2nd‐Neighbor Exchange: Application to EuS

摘要: This paper describes the derivation of exact power series expansions high‐temperature magnetic‐heat capacity Heisenberg ferromagnets having both first‐ and second‐neighbor exchange interactions. The calculations employ general diagramatic techniques developed by Rushbrooke Wood as extended Wojtowicz Joseph to include interaction. All mixed coefficients for terms through fifth inverse temperature have been computed arbitrary spin lattice structure. used obtain certain information on nature interactions in ferromagnetic EuS. By use a spin‐wave analysis Charap has able deduce set values which simultaneously fit low‐temperature magnetization heat data. It found that these same substituted into present theory are capable reproducing data Moruzzi Teaney. result lends considerable support hypothesis EuS is very nearly an ideal ferromagnet.