Effect of off-stoichiometry and site disorder on the properties ofNi3Al: I. Electrical and magneto-transport

Abstract

Electrical resistivity, ρ(T), and longitudinal magnetoresistance, , of ‘as-prepared’ NixAl100−x alloyswith x = 74.3, 74.8, 75.1 and76.1 at.% and ‘annealed’ Ni75.1Al24.9 alloy, measured over wide ranges of temperature and external magnetic field(H), are discussed in the light of existing theoretical models.ρ(T) exhibits a non-Fermi liquid (NFL) behaviour at low temperatures in the range1.7 K≤T≤Tx (where Tx decreases from 25 to 21 K as the Ni concentrationx increases from 74.3 to 75.1 at.%) in the alloys withx<76.1 at.%. Compositional disorder (particularly under-stoichiometry) gives rise tostronger deviations from the Fermi liquid behaviour and widens the temperaturerange over which the NFL behaviour persists whereas site disorder makes theNFL behaviour more prominent, particularly in the stoichiometric composition(Ni3Al), and stabilizes the NFL behaviour in any given compositionover a much wider temperature range. The main contributions toρ(T) and arise from the scattering of conduction electrons from the ‘unconventional’ spinwaves (exchange-enhanced non-propagating spin-density fluctuations) at lowtemperatures (intermediate temperatures and temperatures close to the Curie point,TC). The self-consistent spin fluctuation theory correctly predicts thatH leaves the functionaldependence of ρ on temperature unaltered and quantitatively describes the suppressionof the spin-wave and spin-density fluctuation contributions toρ by H in different temperature regimes.