Magnetic Characteristics of Ni–Pd–Mn Ternary Alloys for “Thermoseed”

Abstract

This paper describes the development of the “Thermoseed,” a thermally self-regulating implant for induction thermocoagulation of brain lesions. The thermoseed should have a low Curie temperature and a high saturation magnetization that will cease heating at a predetermined temperature, i.e., 343–373 K.
In contrast to many nickel base alloys, the saturation magnetization of nickel increases or remains constant with the addition of manganese and/or palladium, in spite of the decrease in the Curie temperature. The Ni–Pd–Mn ternary system introduced by Köster and Sallam has been re-examined, and the composition dependence of both the Curie temperature and the saturation magnetization has been determined in the ternary fcc solid solution range. The desired composition for a thermoseed is selected as the intersection of the saturation magnetization ridge and the desired Curie temperature contour.