Electronic structure of the strongly-exchange-enhanced paramagnet Ni3Ga.

Abstract

The electronic structure of the incipient ferromagnet ${\mathrm{Ni}}_{3}$Ga has been studied by means of the de Haas--van Alphen technique in the magnetic field and temperature ranges 10\ensuremath{\le}H\ensuremath{\le}100 kG and 0.38\ensuremath{\le}T\ensuremath{\le}4.2 K, respectively. Concurrently, first-principles energy bands have been calculated by means of the linear-muffin-tin-orbital method. The calculated Fermi surface consists of four concentric hole sheets centered on the point \ensuremath{\Gamma} of the simple-cubic Brillouin zone. de Haas--van Alphen frequency branches in close agreement with those expected for each of these four sheets have been observed for field directions both in the (100) and (11\ifmmode\bar\else\textasciimacron\fi{}0) planes. The cyclotron masses of these branches, as well as the linear coefficient \ensuremath{\gamma} of the electronic heat capacity, are, however, greater than predicted by our band model, by a factor of between 1.5 and 2.7. Comparison of the measured and calculated magnetic susceptibility yields a Stoner enhancement factor of 98, the highest so far reported in an ordered paramagnetic transition metal, and an enhancement of the quadratic coefficient of the inverse susceptibility \ensuremath{\alpha}=\ensuremath{\partial}${\ensuremath{\chi}}^{\mathrm{\ensuremath{-}}1}$(T)/\ensuremath{\partial}(${T}^{2}$), of over 8. The strong renormalization of \ensuremath{\gamma} and \ensuremath{\alpha} points to the importance of exchange-enhanced spin fluctuations for this material, as previously reported in the weak itinerant-electron ferromagnet ${\mathrm{Ni}}_{3}$Al.