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Notes: The temperature dependence of the susceptibility χ(T)=M(T)/H of Cr1−xMnx((very-much-less-than)0.1〈x〈8% Mn) alloys in the range 5〈T〈400 K and in fields up to 55 kOe, measured with a SQUID magnetometer, and hysteresis of the magnetization M(H) show typical spin-glass (SG) behavior. After zero-field cooling (ZFC), χ(T) exhibits the low-T maximum typical of a SG, while cooling in the measuring field (FC) gives quite different behavior. In some cases, when measuring at low field, χ(5 K) is 10× larger in the FC state than in the ZFC state. The temperature of the irreversibility limit decreases with increasing field. All our CrMn alloys show nonlinear field dependence of M(H), with pronounced hysteresis and decay of the remanent M with time. On the other hand, these alloys exhibit properties that are essentially different from those of all other metallic spin glasses: (1) the linear scaling law based on the RKKY interaction between magnetic impurities in a typical SG is not obeyed, and indeed the temperature of the maximum in χ(T) is essentially independent of Mn concentration, which shows that formation of the SG state does not depend on the distance between the Mn atoms; (2) the maximum in χ(T) in the alloy containing only a trace of Mn ((very-much-less-than)0.1%) is at about 40 K, a temperature at least an order of magnitude larger than that in CuMn and other metallic SG with about 0.1% impurity concentration; (3) χ(T) obeys a Curie–Weiss law above the Neel temperature, but not below, which shows that the Mn moment is frozen in the spin-density-wave (SDW) matrixWe propose a model to explain this unusual behavior, in which the SG state is formed, not as a result of frustration of the Mn impurity moments, but through the frustration of the moments of the itinerant electrons of the host Cr. At low temperatures the frozen Mn moments pin the SDW, which gives rise to frustration surfaces between adjacent domains having different phase of the SDW. This effect depends only on the T-dependent interaction between the Mn moment and its neighbors, and thus is independent of the Mn concentration. © 1996 American Institute of Physics.

Notes: The pressure dependence of the resistivity ρ(T) of (Cr+2.7 at. % Fe)98V2 is measured, following a previous study of the temperature dependence of ρ(T) in the spin-density-wave (SDW) alloy system, (Cr+2.7 at. % Fe)1−x(V,Mn)x. The minimum in ρ(T) in the V-doped alloys seen at T(approximately-greater-than)TN for x〉1 at. % is found to move to lower temperatures under pressure p in the alloy containing 2 at. % V, decreasing in magnitude, and eventually, as the Neel temperature TN goes to zero at p(approximate)10 kbar, becoming a very shallow minimum followed by a maximum and a rapid decrease as T→4.2 K. This latter behavior in the paramagnetic phase is believed to be due to the Kondo effect, while the pressure dependent minimum in ρ(T) in the SDW phase is a manifestation of impurity resonance scattering. © 1997 American Institute of Physics.

Notes: The temperature dependence of the magnetic susceptibility χ(T) of seven Cr1−xFex alloys measured around the Neel transition shows a strong first-order transition at the Neel temperature TN for the Fe content, x=2.7 and 3.7 at. % Fe, greater than the triple-point concentration, xL=2.4 at. % Fe, where the paramagnetic, incommensurate-, and commensurate-spin-density-wave (ISDW and CSDW) phases meet. Alloys with x(approximately-less-than)xL (x=2.0 and 2.15 at. % Fe) show a weak transition at TN and a strong first-order transition at TIC (the ISDW–CSDW transition). The magnetic phase diagram of the Cr1−xFex alloy system below xL is re-interpreted in light of these results and the neutron diffraction work. The coexistence of the CSDW and ISDW phases in the mixed state below the branch TIC(x) of the first-order incommensurate-commensurate (IC) phase transition, for values of x well below xL, may result from anisotropy of the large strain at TIC. © 1997 American Institute of Physics.

Notes: While pure chromium undergoes a first-order antiferromagnetic transition, thermal expansion measurements have indicated that the addition of small amounts of vanadium and molybdenum make the Néel transition continuous. A neutron diffraction study of a single crystal of Cr(0.5% V) showed no discontinuity in magnetic Bragg satellite intensity at the Néel temperature, TN=254 K, that would indicate a first-order transition. Complicated behavior of the satellite intensities near the transition temperature is attributed to inhomogeneous strain in the sample. The satellite intensity showed a linear temperature dependence over a range of at least 100 K below TN.

Notes: A single crystal of Cr+0.5 at. % V was field cooled through its Néel temperature TN(approximately-equal-to) 260 K, with a field B=12 T, along a cube axis to produce a single-Q state. The attenuation α was measured for 10-MHz longitudinal ultrasound propagating parallel and perpendicular to Q, and also in the non-field-cooled poly-Q state. The resultant anisotropy in the change in α at the spin-flip temperature TSF(approximately-equal-to)40 K, shows the sample to be largely single-Q, but its nature suggests that the change of the magnetic structure at the low-temperature phase transition may differ from that in pure Cr.