Étude de l'antiferromagnétisme helicoidal de MnAu2 par diffraction de neutrons

Microwave absorption in terbium, erbium and MnAu₂ at selected frequencies from 20-120 GHz

“…For the small resonance fields (~3 kOe} of the 11 surface 11 ferromagnetic peak at our experimental frequency, we would expect these H}=O values of cr to be almost correct. As can be seen by 1 ine A in Figure 14, the temperature dependence of our low field data is well explained by assuming the data are due to ferromagnetic resonance with HA=23 kOe, or about half the HA=45 kOe value ·determined by our bulk ferromagnetic resonance studies described pre- We call the low field peaks 11 surface 11 ferromagnetic resonance because at the field at which the resonance occurs the bulk sample Is in a spiral structure as determined by neutron diffraction (37).…”

“…++ bined at T=O K, however, the predicted magnetic moment on a given Mn ion is g~S=4.8 ~' or more than I ~ greater than the experimentally observed magnetic moment using neutron diffraction (37). We expect that part of this discrepancy is due to zero point motion of the spins having an energy given by the second term in Equation 26, but if the zero point motion accounts for the complete discrepancy, the magnetic moment of a given spin along its equilibrium direction at T=O K Is about 75% of the value it would have.without zero point motion.…”

“…The 11 sp ira 1 · phase 11 paramagnetic resona nee may we 11 turn out to be due to a bulk paramagnetic phenomenon in the spiral phase of MnAu 2 where a component of the magnetic moment might be disordered (37).…”

Collapse and control of theMnAu2spin-spiral state through pressure and doping

“…The tetragonal material MnAu 2 is one of the oldest known spin-spiral materials [1][2][3], with a Néel temperature of T N = 363 K [1] and a local Mn moment of 3.5µ B [3,4]. The magnetic ground state consists of inplane ferromagnetic Mn layers with a screw-type pattern around the tetragonal c axis, which can be described using the spiral angle θ [this is equivalent to the wave vector q = (0, 0, q z ), where θ = q z c/2].…”

“…The magnetic ground state consists of inplane ferromagnetic Mn layers with a screw-type pattern around the tetragonal c axis, which can be described using the spiral angle θ [this is equivalent to the wave vector q = (0, 0, q z ), where θ = q z c/2]. Neutron diffraction measurements [3,5,6] find that θ has a weak dependence on temperature, increasing slightly with increasing temperature [θ(77 K) = 47…”