Spin-Density-Wave Distributions in Chromium and Chromium Alloys

Abstract

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Lattice Anisotropy in Antiferromagnetic Chromium

“…These are (c^c 2 )/c x = (3.5±0.2)xl0" 6 , (b x -a 2 )/b x = (-4.7 ±0.2)xi0- 6 , and (a x -a 2 )/a x = (-0.2±0.2)x 10~6. From these values we calculate a volume change at T F of (^-^2)/^=-1.4xi0~6 which, using the value of dT F /dP reported by Umebayashi et al, 19 corresponds to a latent heat of 4.lx 10~4 J/g, in good agreement with the estimate of Street et al 7 From our measurements we are unable to decide whether the small change Aa/a at T F is truly characteristic of the transition or a result of a small number of spins remaining in the measuring direction due to spin-pinning effects. For if \\Z= 50 kOe we measure Aa/a--0.4X 10~6, whereas for H \\Z= 100 kOe we measure Aa/a = -0.2 x 10 ~6.…”

“…It was found that the depression of T F with H II C § was quadratic in H and that a field of 100 kOe applied parallel to C$ depressed T F to about 105 °K in good agreement with the work of Street et al 7 Therefore a temperature of 100°K (below the depressed T F ) was chosen for the ^-switching experiment, in which the field was increased from 0 to 100 kOe parallel to Cj. Although ideally one would like to perform the (^-switching experiment on a perfect single-^ crystal, it appears that increased perfection of the single-C § state (achieved by using a higher H c ) requires larger fields to achieve any measurable C § switching.…”

Chromium at high pressures: Weak coupling and strong fluctuations in an itinerant antiferromagnet

“…3͑a͒ was oriented in the cell with the L cubic direction along the diamond compression axis. Given the known dependence of the Q domains on uniaxial stress, 30,31 one would expect that anisotropic stress resulting from the glassy pressure medium would pin the domain configuration into a particular state, most likely along the compression axis. By using our measured value of ͑1 / a 0 ͒͑da / dP͒ = −1.76ϫ 10 −3 GPa −1 for the compressibility of Cr at low temperature and the known value of ⌬a / a 0 =−17ϫ 10 −6 for the tetragonal strain parallel to Q at low temperature, 30 we estimate that the uniaxial stresses affecting our sample are no greater than 0.01 GPa whenever any single domain does not occupy 99% or more of the total volume.…”

Antiferromagnetism in a Cr86Ru14 alloy

“…Hysteresis effects were previously also observed [20] in the v L -p curves of single crystalline Cr and were ascribed to the poly-Q domain structure. Other unresolved anomalous behaviours in the magnetic ordering in polycrystalline pure Cr are absence of hysteresis in the electrical resistivity and Young's modulus in the vicinity of T N [14], in contrast to earlier studies [16].…”

“…The influence of the Q-domain state on the elastic constants, and therefore the ultrasonic wave velocities of CSDW Cr-Ru alloys have not been specifically studied as part of this study. Studies of ISDW pure Cr found [15][16][17] that the elastic constants were significantly influenced by changes of the Q-domain distribution induced by applied magnetic fields or stresses.…”