A.M. Mulders

Crystal fields and magnetic interactions in TmT2Si2 (T = Co, Ni, Cu)

An inelastic neutron scattering and 166Er Mossbauer spectroscopy study was performed on ErCo2Si2 and a 169Tm Mossbauer spectroscopy study was performed on TmT2Si2 (T = Co and Ni). The saturation Er moment in ErCo2Si2 was found to be 7.8 µB and the saturation Tm moment in TmCo2Si2 was determined to be 6.5 µB. A crystal field interpretation of ErCo2Si2 and TmT2Si2 (T = Co and Ni) is presented and, together with a new interpretation for existing data for T = Cu, trends in the crystal field parameters within the TmT2Si2 series are presented.

High-field magnetization in the diluted quasi-two-dimensional Heisenberg antiferromagnet Mn1−xZnxPS3

Magnetization of Mn1−xZnxPS3 in fields up to 35 T is presented. Small amounts of weakly bound moments have been observed for the more diluted compounds with a preferential orientation equal to that of the long-range antiferromagnetic order. The width of the spin-flop transition can be described by static domain wall broadening which is limited by the magnetic domain size. We estimate an average domain size of 200–250 nm.

The Orientation of the Antiferromagnetic Order in FePS3

Mössbauer spectroscopy was performed on FePS3. Magnetic moments of a single crystal were found to be parallel to the z-axis at temperatures below 96 K. The internal hyperfine field was 9.64 T at 10 K. The EFG was calculated to be at an angle of 17(2)° to the z-direction.

Muon spin dynamics and sites in GdNi5

In GdNi5, the muon localizes at the 3f interstitial site and below ∼80K a second muon site becomes populated, the so-called 6ring site. This ring site is metastable and the muon hops to the 3f site. We determine the mean time of stay of the muon in the ring site and show that it is governed by a multi-phonon quantum diffusion process. The coincidence energy is measured to be Ea=272(10)K and the tunneling matrix element J=0.11(2)meV.

Magnetism and superconductivity of UPt3 by muon spin techniques

We summarize our recent μSR results on the magnetic and superconducting properties of the heavy-fermion superconductor UPt3. Whereas zero-field measurements show no signature of the superconducting and magnetic phase transitions, the experiments in high transverse field evidence the presence of two inequivalent magnetic regions for temperatures ranging from 0.2 to 115 K with an anomaly near the magnetic transition. From low transverse field experiments in the low-temperature superconducting phase (B phase), we deduce the temperature dependence of the superfluid densities. We briefly discuss all these results in relation to those obtained for other compounds of this family.

Zero- and longitudinal-field muon spin depolarization measurements of CeNiSn

Abstract We report on zero- and longitudinal-field muon spin depolarization measurements performed on single crystals of the Kondo insulator CeNiSn. The initial muon beam polarization is parallel to the a crystal axis. Going down in temperature, we observe in zero field a monotonous increase of the exponential damping rate starting at ∼20 K . In longitudinal field measurements the damping rate drops to zero at a few mT, reflecting a quasi-static field distribution at the muon site. Contrary to previously published results, our data do not allow to safely determine whether the observed increase of depolarization at low temperature originates from the electronic–magnetic correlations or from nuclear magnetic moments of the compound.

Muon spin relaxation in uniaxial ferromagnets

Abstract We present μSR data recorded on two ferromagnets: GdNi 5 and ErNi 5 . Depending on the anisotropy of the magnet, the muon spin lattice relaxation rate, λ, is controlled at low temperature either by a magnon process or a phonon process.

Muon localization along a six-fold ring-shaped site and muon quantum hopping in GdNi5

Abstract In GdNi5, the muon localizes at the 3f interstitial site and below ∼80 K a second muon site becomes populated, either at the 6m or 6k site. These latter sites are located in a ring surrounding the (0, 0, 1 2 ) site and the muon occupies all six sites within the time range of the experiment (10−9 s). This ring site is metastable and the muon hops to the preferred 3f site. We determine the mean time of stay of the muon in the ring site and show that it is governed by a multi-phonon quantum diffusion process. The coincidence energy is measured to be Ea=272 (10) K and the tunneling matrix element J=0.11 (2) meV.