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Abstract:
It was recently suggested that for the Cr1-xAlx alloy system the
Sommerfeld specific heat coefficient (gamma) as a function of x may peak
at the triple point (TP) concentration (x(t)) of the x-T magnetic phase
diagram. The TP at (x(t), T-t) represents the intersection point of
three magnetic phase transition lines at which incommensurate (I) and
commensurate (C) spin-density-wave (SDW) phases are expected to coexist
with the paramagnetic (P) phase. A comprehensive experimental study on
the physical properties of single crystalline Cr1-xAlx alloys in the
concentration range 0 <= x <= 0.034, that encloses x(t), is reported
here for further investigations of the above conjecture and possible
anomalous behaviour in other physical properties near x(t). The
measurements include the electrical resistivity (rho), Seebeck
coefficient (S), specific heat (C-p), Hall coefficient (R-H), magnetic
susceptibility (chi) and thermal conductivity (kappa). All these
properties, except for kappa, depict anomalous temperature and
concentration dependencies of SDW origin for x close to x(t). The
present study indicates a value of x(t) rather close to x = 0.022. The
x-dependence of gamma exhibits an extraordinary large and sharp peak
near this concentration. This observation is interpreted as indication
that the temperature of the TP is likely situated at 0 K. A new magnetic
phase diagram is therefore proposed for the Cr1-xAlx alloy system for x
in the region of x(t). This study presents novel experimental evidence
of exceptional anomalous magnetic behaviour around the TP concentration
of the Cr1-xAlx system. It should incite similar studies on other Cr
alloy systems with a TP on their magnetic phase diagrams. (C) 2014
Elsevier B. V. All rights reserved.
