E. Fawcett

Possible tricritical point in dilute chromium alloys

Measurements of thermal expansion through the Neel transition show that, when V, Mo or Mn atoms are substituted in the Cr lattice, the nature of the antiferromagnetic transition changes from weak first order in pure Cr to continuous. The possible tricritical point in CrV is close to 0.2 at.% V.

Magnetic behaviour in the spin-density-wave phase of ( x < 20% Mn) alloys

The magnetic susceptibilities of twelve samples in the alloy system , with x ranging from to 19.4% Mn, are measured in the temperature range , in applied fields in the range Oe, after cooling in zero field and in the measuring field. The field dependence of the magnetization M(H) is measured at T = 5 K in the range kOe. The magnetic behaviour is characteristic of a spin glass, with hysteresis of M(H) and also hysteresis between the field-cooled and zero-field-cooled states, a peak in for the zero-field-cooled state, and relaxation of M as the logarithm of time when H is changed at low temperature. Unlike a typical spin glass, however, the peak in in the zero-field-cooled state is at roughly the same temperature (between 25 and 40 K) for all concentrations, and Curie - Weiss paramagnetism is seen at higher temperatures only for Mn. The Curie constant increases by an order of magnitude between x = 11.2 and 13.5% Mn, corresponding perhaps to a change in the atomic short-range order.

Magnetic phase diagrams and impurity resonance scattering of CrFe and CrSi, and their ternary alloys with V and Mn: II. Experiment: thermal expansion and the temperature and pressure dependence of resistivity

Abstract Experiments are described and the resultant data presented for the temperature dependence of the resistivity ϱ(T) and the thermal expansion ϵ(T) of the ternary alloy systems (Cr+2.7 at% Fe)1−z(V,Mn)z, (Cr+1.5 at% Fe)1−z(V,Mn) z and (Cr+1.3 at% Si)1−z(V,Mn)z, in the range of temperature from T

Magnetic Gruneisen parameters in chromium

Gruneisen parameters are defined and determined for Cr in the paramagnetic phase, at and below the Neel temperature, at low temperatures and at zero temperature, by comparing the temperature dependence of the thermophysical properties, as well as from direct pressure measurements (the latter also for dilute antiferromagnetic alloys of Cr with V or Mo). The values are all large and negative, and in particular in the paramagnetic phase the logarithmic volume dependence of the characteristic spin fluctuation temperature is 155.

Elastic constants of antiferromagnetic chromium

The temperature dependence of the elastic constants of antiferromagnetic chromium in the poly-Q, single-Q and single-S single-Q states has been measured between temperatures in a little above the Neel temperature TN and below the spin-flip temperature. The discontinuities in the elastic constants at TN agree with the predictions of mean-field theory, and their temperature dependence in the transverse spin density wave phase agree with the predictions of a thermodynamic model, if TN is assumed to depend mainly on volume strain omega and to be linear in omega .

Thermal expansion of Cr and Cr-V alloys

At low temperatures, the linear expansion coefficient α of a Cr + 0.5% V alloy is similar to that of chromium, i.e. 1010α = -37 T + 0.02 T3K−1 (T<30 K), giving an electronic and/or magnetic Gruneisen parameter γem ≈ -10. For the non-magnetic alloy Cr + 5% V, 1010α = 11 T + 0.03 T3K−1 and γe ≈ 2.0. At higher temperatures, α (T) for the 5% alloy increases monotonically and is significantly larger than for pure Cr up to 520 K; α(T) for the latter shows a negative cusp at 311 K with a first-order transition.

Magnetic phase diagrams and impurity resonance scattering of CrFe and CrSi and their ternary alloys with V and Mn: III. Magnetic phase diagrams in the composition-temperature and the pressure-temperature planes

Abstract The magnetic phase diagrams in the composition-temperature and pressure-temperature planes of antiferromagnetic spin-density-wave (SDW) Cr1−xFex and Cr1−xSix alloys are constructed from published data, and new experimental res ults for the temperature dependence of the electrical resistivity and thermal expansion in ternary alloys are employed to study the effect of changing the Fermi level by doping with V or Mn. These systems exhibit features unique among the antiferromagnetic SDW Cr alloys, including a re-entrant commensurate SDW phase and strong first-order transitions to this phase, which show nevertheless the parallelism often seen in Cr alloys between the effects of applying pressure and reducing the electron concentration.

Temperature dependence of critical neutron scattering in Cr+0.2 at. % V and chromium

The dynamic magnetic susceptibilities, χ(Q,ω), of Cr+0.2 at. % V and chromium were measured in the temperature range (TN−15 K)<(TN+20 K) by neutron scattering. Here, χ (Q,ω) of Cr+0.2 at. % V is clearly incommensurate, in contrast to the apparently commensurate inelastic scattering seen in pure chromium. The observed form of the scattering for each material does not qualitatively change in going from above TN (paramagnetic) to below it (antiferromagnetic). Since no discontinuity in elastic magnetic intensity was observed in the alloy crystal, analysis in terms of the critical phenomena of a second‐order phase transition can now be attempted.

Paramagnetostriction of transition metals

Abstract Measurements of the magnetostriction of cubic paramagnetic transition metals are reviewed and new data for the hexagonal metals Zr, Ti and Sc are presented. In Pd and Pd Rh alloys the large volume magnetostriction is associated with the exchange-enhanced spin susceptibility, while the explanation for the relatively large shape magnetostriction is still in question. In Mo and W the anisotropy of the magnetostriction is attributed to the orbital susceptibility, but in that case the shape magnetostriction for V and Sc is surprisingly small.

The magnetic phase diagram and transport properties of

We have used resistivity measurements to study the magnetic phase diagram of the itinerant antiferromagnet in the temperature range from 0.3 - 300 K in magnetic fields up to 16 T. In contrast to theoretical predictions, the incommensurate spin-density-wave phase is found to be stable at least up to 16 T, with an estimated critical field of . We have also studied the low-temperature magnetoresistance in the [100], [110], and [001] directions. The transverse magnetoresistance is well described by a power law for magnetic fields above 1 T with no saturation observed at high fields. We discuss our results in terms of the magnetic structure and the calculated electronic band-structure of . We have also observed, for the first time in this compound, Shubnikov - de Haas oscillations in the transverse magnetoresistance with a frequency of for a magnetic field along [001].