Giant ΔE effect and elinvar characteristics in amorphous FeB binary alloys

Abstract

Amorphous Fe100−xBx (11.5 ≦ x ≦ 22) binary alloys are made in a ribbon form from melts by a single roller quenching method, and the temperature dependence of Young's modulus is measured as functions of the boron content and the annealing temperature. In the alloys used, Elinvar characteristics are found over a wide range between −100°C and the Curie temperature. The ΔE effect and the linear saturation magnetostriction largely depend on the boron content and the annealing temperature indicating maximum values of about 70% and about 50 × 10−6, respectively. Temperature coefficient of delay time calculated from the coefficients of thermal expansion and Young's modulus is extremely small around room temperature because these alloys exhibit simultaneously Invar and Elinvar characteristics.

A new mechanism for low and temperature-independent elastic modulus

“…Since then materials of similar anomaly have been reported in ferromagnetic (e.g., FeSiB amorphous alloys4) and anti-ferromagnetic (e.g., MnNiCr alloys5) systems and they have found many applications in advanced instrumentation that requires high mechanical accuracy such as filter chronometer, seismographs, pressure gauges, mechanical vibrators and delay lines678. Mechanistic studies9101112 have focused on magnetic phase transitions and the associated magnetoelastic interactions as the possible physical origin of the Elinvar anomaly (Elinvar for short hereafter). For example, the transition between two spin states upon cooling could result in significant elastic modulus softening, which is able to compensate the normal elastic modulus hardening on cooling and leads to Elinvar11.…”