Magnetic order and moment stability in YMn₂

Abstract

High-resolution neutron powder diffraction and tr-v-e field ~S R mea. surements have been used to examine the nature of the magnetic and structural transition at 100 K in YMn2. The neutron measurements indicate a first-order hysteretic transition occurring at 92.5 K on cooling and 108 K on warming. The low-temperat-phase is tetragonal (./a = 0.995) and antiferromagnetic with localized Mn moments of 2.8 pg ordering i n a long-wavelength helix characterized by an antiferromaeetic translation vector (T, 7') 1) where T = 0.018 and T' = 0.003. The high-temperat-phase is cubic and Pauli paramagnetic, The collapse of the Mn moment at the transition is accompanied by a 5% decrease in the cell volume. In the paramagnetic state of YMn? measurement of the muon transverse relaxation rate reveals an underlying second-order transition which we assodate with the critical slowing of longitudinal spin fluctuations as the transition temperatureis approached.

Order by Distortion and String Modes in Pyrochlore Antiferromagnets

“…In one family of cases the spin-Peierls transition can be first order, as indeed observed in many pyrochlore antiferromagnets [7][8][9][10][11][12].…”

Electronic structure and magnetic examination of ScMn2 single crystal

“…For the compounds with a distance greater than the critical one a localized magnetic moment on the Mn sites is observed (even 2.7 B for YMn 2 [1]). For the RMn 2 compounds with a distance smaller than the critical one, no magnetic moment on the Mn sites is observed, as in the case of the ErMn 2 compound [2].…”

“…The effect of replacing Y by Sc is that Y 1−x Sc x Mn 2 is a paramagnet [9] because of the decrease of the Mn-Mn distance.…”

Quasicritical Behaviour of the NMR and µSR Relaxation in YMn2Dx

“…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.…”