Untitled

Abstract

Measurements are reported of the temperature dependence of the elastic constants, ultrasonic attenuation and thermal expansion of dilute Cr - Ga alloy single crystals containing 0.16, 0.42 and 0.88 at.% Ga. Well defined magnetic anomalies were observed in all of these physical properties at the Néel temperature , at the incommensurate - commensurate (I - C) spin-density-wave (SDW) transition temperature and at the spin-flip transition temperature . The complete magnetic phase diagram of the alloy system has been determined for x < 1 at.% Ga from the temperatures of these anomalies. The magnetovolume and the magnetic component to the bulk modulus were both found to vary as , as predicted by theory, in the ISDW phases of all three of the crystals. Values of the pressure derivatives of for the crystals containing 0.16 at.% Ga and 0.42 at.% Ga were calculated from the results for and calculated for the Cr + 0.16 at.% Ga crystal compares very well with the value obtained from direct high-pressure measurements. High-pressure measurements have not been made on the Cr + 0.42 at.% Ga crystal for a comparison. The value calculated from and for Cr + 0.88 at.% Ga does not compare well with obtained from direct high-pressure measurements. This may point to inadequacies in the thermodynamic model used for the calculations. Predictions of microscopic theories for the temperature dependence of the ultrasonic attenuation, magnetovolume and the magnetic components of the elastic constants close to do not fit the present measurements.

Influence of V and Mn doping on the electrical transport properties of a Cr+1.2at.% Ga alloy

“…13) on the present polycrystalline Cr 0.988 Ga 0.012 alloy show a welldefined large peak in the α-T curve at T IC , similar to that found in a series of polycrystalline Cr-Ga alloys of a previous study [26]. Recent [15] studies on a Cr + 0.88 at.% Ga alloy single crystal, however, show an opposite effect in that a minimum instead of a maximum is observed in the α-T curve of such a crystal. Clearly, more work is needed on the SDW properties of Cr-Ga alloys, both in polycrystalline and single crystalline forms, to get a better understanding of the abovementioned anomalous behaviour of α and ρ around T IC in them.…”

“…These [7,15] are contributions from electron-phonon scattering, the reduction of the number of current carriers due to the appearance of the SDW energy gap below T N , resonant impurity scattering and from effects of spin-fluctuations. The electrical resistivity of a Cr alloy can thus be written as [15] ρ exp (T ) = ρ 0 res + ρ res (T ) +…”

“…The energy gap function ∆(T )/∆(0) is taken as the BCS gap function [15,16]. The electron-phonon resistivity of an ideal nonmagnetic Cr alloy is represented by…”

“…The parameter α is an indication of the nesting fraction of the electron and hole Fermi surface sheets that are annihilated on SDW formation in the alloys. For several dilute Cr alloy systems that are in the ISDW phase at 0 K, the parameter α is in the order of 0.10-0.35 [15,16].…”

A Time- and Position-Sensitive Detector using a Resistive Film Anode Combined with a “Modified Backgammon with Weighted Capacitors” Readout Pad

“…We [14][15][16] recently succeeded in growing good quality Cr-Si and Cr-Ga alloy single crystals and ρ-T measurements up to about 1000 K on these crystals are reported here. Three Cr-Si and three Cr-Ga alloy single crystals were studied.…”