Specific heat and modulated magnetic structures in the HoNisub(0.5)Cusub(0.5) and ErNisub(0.6)Cusub(0.4) compounds

Specific heat measurements performed on HoNisub(0.5)Cusub(0.5) and ErNisub(0.6)Cusub(0.4) have confirmed the role of the rare earth nature on the thermal stability of modulated magnetic structures. With non Kramers ions (Ho for instance) lying in a very low symmetry site a modulated structure can remain stable down to zero Kelvin; the magnetic moment being induced by the exchange field, no entropy is associated with the modulation. With Kramers ions (Er for instance), for which an intrinsic moment always exists, a modulated structure transforms at low temperature into an antiphase structure. (author)