Ferromagnetic Metals in High Magnetic Fields

. High-field susceptibility results ~re presented for MOssbauer measurements on iron at low temperatures m field.s up ~o 13~ kOe and magnetIZatIOn measurements on iron and nickel single crystals in fields up to 148 kOe WIth vibratmg sample magneto~eters. The Mossbauer measurements give the hyperfine field H n = Hint(HO-1!I:!M) +AH, where !lint IS the hyperfine field at zero applied field,Ho is the applied field,HDM is the demagnetrzmg field, a~.d AH IS a term which ,:ould reflect a change in the magnetization at high field, Le., An./Hn=A~/M. T~e Mossbauer results at 4.2 K are equivalent to x=2±7X1o-6 emu/cc. The magneti. zatlO~ ex,?enments grve x:S;4X10-6 for iron and x:S;1.1XlO-6 for nickel at 4.2°K. We discuss the various c?ntnbutlO.ns to the to~al.sus.ceptibilityX, give ~stimates of. Xd based on theoretical band calculations, and dISCUSS ~anous uncert~mtres m bo~h the ~heoretrcalcalculatrons and in values of the molecular field param­ eter which ma.ke detail~d .compansons dIfficult. Finally, we compare with predictions based on Herring's phenomenolOgical descnptron of X for ferromagnets.