S. J. Harker

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.

Magnetic anisotropy of Pm impurity in rare earth–nickel compound

Low-temperature nuclear orientation was applied to study hyperfine interactions of 142Pr, 147Nd and 143,144Pm nuclei in Pr0.5Nd0.5Ni single crystal. Angular distributions, temperature dependence and external magnetic field effects on the γ-ray anisotropy are presented. A Nd-Pm exchange interaction seems to dominate the magnetic properties of Pm ions in this system.

Radiative detection of NMR studies of domain nuclei in enriched ferromagnetic iron

Combined host (∼95 at% enriched stable 57Fe) and very dilute impurity (∼0.01 at% radioactive 60Co) NMR signals have been obtained on the one sample of polycrystalline Fe foil utilising perturbations to the gamma anisotropy from in situ thermally oriented 60Co nuclei for both resonances. The NMR-TDNO signals on the 57Fe sites have been followed down to applied magnetic fields well below the host magnetic saturation and exhibited two distinct components; a strong, narrow homogeneous signal, superimposed over a broader inhomogeneous signal. The impurity 60Co57Fe inhomogeneous resonance has been studied with three pulse NMRON and the irreversible decay of the nuclear spin echo measured as a function of applied magnetic field.

Crystal-field interaction at the thulium site in

Mossbauer spectroscopy is used to monitor the quadrupole interaction for the superconductor as a function of temperature. Qualitative comparison with other results supports earlier claims that the rank-2 crystal-field contribution lies between that for and that for . However, there is quantitative disagreement with crystal-field parameters determined elsewhere for .

Nuclear Orientation Studies of Magnetism in Single Crystal Pr0.5Nd0.5Ni

The angular distributions of γ-rays from 142Pr, 147Nd and 144Pm in Pr0.5Nd0.5Ni were investigated by means of low-temperature nuclear orientation. The results show that the Pr and Nd electronic moments order along the c- and a-axis, respectively. Pm ions introduced as a very dilute magnetic impurity, preferentially align with the Nd ions.

NMRON Study of Magnetically Ordered (166mHo)HoF3

A NMRON study of magnetically ordered HoF3 using in-situ neutron activated 166mHo (I=7) isoelectronic probes in a spherical single crystal is presented. The optimal sensitivity to resonant change in the gamma-ray anisotropy of the 810 keV daughter gamma-ray emission has been utilised to track the lowest nuclear Zeeman substate resonance over an applied magnetic field range from 0.300 to 0.524 T, corresponding to the frequency range 1.56 to 1.78 GHz. The 2nd lowest substate resonance has also been observed at 0.3 T leading to a value P/h=−32.9(14) MHz for the 166mHo quadrupolar splitting which is consistent with predictions of a dominant negative pseudo-quadrupole interaction in this system. The Ho3+ electronic moment, in zero applied magnetic field, is projected to be 16% smaller than measured previously with neutron diffraction.

A low-temperature study of electronic and nuclear states in YbVO4 using NMR thermally detected by nuclear orientation

Abstract In this paper, we report on the applied magnetic field dependence of the 171Yb NMR thermally detected by nuclear orientation in the antiferromagnetic insulator YbVO4 ( T N =93 mK ), at millikelvin temperatures.

A low temperature study of antiferromagnetic YbVO4 by NMR thermally detected by nuclear orientation

NMR-TDNO results using an external 60CoCo (hcp) nuclear orientation thermometer for non-irradiated, single crystal, antiferromagnetic YbVO4 are compared with those obtained earlier with neutron activated samples using both internal and external γ-ray thermometers. Detailed comparisons are made for the 171Yb (I=1/2, 14.31% abundant) stable nucleus. This strongly asymmetric, largely homogeneous, resonance lineshape was retained and is readily power broadened. Extremely broad, field-dependent homogeneous thermometric responses are observed in the expected frequency range for the quadrupolar stable nucleus 173Yb (I=5/2, 16.13% abundant) for both irradiated and non-irradiated samples.