The magnetic and structural properties of YΜn 2 are strongly influenced by introduction of hydrogen (deuterium) in the structure, however, it only slightly modifies the noncollinear antiferromagnetic structure of the compound. The temperature dependences of the NMR relaxation times T1 and Τ2 of deuterium and the zero-field relaxation of muons in YΜn2 D x were measured at temperatures above the magnetic ordering temperature TN. The corresponding relaxation rates are described by the empirical expres- The C15 Laves phase compound YΜn2 and its hydrides (deuterides) have very intriguing properties above their magnetic ordering temperature TN. The NMR relaxation times Τι and Τ2 of deuterium and the muon depolarisation rate λ of these materials exhibit a critical divergence as TN is approached from above [1][2][3]. It is interesting that their temperature dependence above TN can be described by nearly the same function of temperature Τ where δ = (Τ -TN )/TN is the reduced temperature, the exponent n depends linearly on the deuterium concentration x and the constant prefactor of course depends on the quantity under consideration. The dependence of n on x is shown in Fig. 1. We call the behaviour described by Eq. (1) "quasicritical" , because the function F(δ) has a singularity when Τ approaches the critical temperature TN but on the other hand the true critical exponent should not depend on the chemical composition of the material but only on the model Hamiltonian [4]. Thus we have to look for another formula which would explain this behaviour. It is clear that spin fluctuations play an important role in the vicinity of the temperature where the (867)

Qcalc bQcm) 0.12 0.55 129 0.18 0.55 128 0 . 2 4 0.55 137 0.28 0 . 5 4 138 0.32 0.53 142 0 . 3 7 0.52 147 0. 70 0.48 191 m n Q (u62cm) at 4 . 2 K 110 130 136 139 142 153 330 exP phys. stat. sol. (b) 125, K17l (1984) Amorphous FeB alloys have been extensively studied for the last years because of their interesting mechanical, electrical, and magnetic properties. There are, however, surprisingly few works dealing with a systematic investigation of the dependence of the electrical resistivity of these alloys on concentration (/l/ and references therein). This note presents new measurements of their resistivity at liquid helium temperature and calculations which explain the results within the diffraction model. Our samples of Fey -,BX alloys were prepared a s thin films by means of the rf sputtering technique. The amorphous state was confirmed in a wide range of boron concentration 0.12 5 x 5 0.70 by electron diffraction microscopy The resistivity was measured by the four-probe method at 4 . 2 K. Further experimental details can be found in /1/ and /2/. Results a r e reported in the table. T a b l e 1 Calculated and experimental resistivity for various boron concentrations x 1 ) al.

A calculation of the effects of spin -orbit interaction on electron transport in 3D disordered systems is presented. We use the Wigner density matrix to construct self-consistent transport equations which can be used to discuss weak localization (quantum interference) effects and even strong localization. The formula for the transport relaxation time has been obtained. The change of the resistivity due to spin-orbit interaction is negative in agreement with experiment.

Self-consistent, general potential, electronic structure calculations have been performed for the Laves phase compound YMn 2 and its hydrides YMn 2 H x (x = 0.5 and 1.0). The parent material, YMn 2 , is found to be an itinerant antiferromagnet with a magnetic moment of 2.6µ B per Mn atom whereas for the hydrides an additional ferrimagnetic component appears. This is in good agreement with experiment. The dependence of the calculated atom-projected magnetic moments and hyperfine fields on the Mn-H interaction is analysed. We have also calculated the total energy for three different H positions and established that the lowest energy is found for the experimentally observed position.

The Laves phase‐type compounds of yttrium and rare earths with manganese (RMn2) easily absorb hydrogen which locates at the interstitial sites. It is well known that the lattice expands with increasing hydrogen concentration and the volume increases up to about 30%. The increase of the unit volume is nonlinear as a function of hydrogen content. To explain this behaviour a model in which the volume changes were correlated with the changes of the bulk modulus with hydrogen concentration was proposed by Hirata and co‐workers. This model describes properly the initial volume increase, but does not reflect the changes at higher concentrations. For the hydrides with R = Y, Gd, Er, Dy, Tb, Ho at x ≈ 3 the volume of AB3 interstitials becomes large enough for hydrogen to enter. According to this observation we extended this model. We show that the calculated volume expansion fits very well to the experimental data for RMn2 (R = Y, Gd, Dy, Tb, Ho). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)