Review on magnetic and related properties of RTX compounds

A review of the muon spin rotation and relaxation studies on magnetic materials published from July 1993 is presented. It covers the investigation of magnetic phase diagrams, that of spin dynamics and the analysis of the magnetic properties of superconductors. We have chosen to focus on selected experimental works in these different topics. In addition, a list of published works is provided.

https://iopscience.iop.org/article/10.1088/0953-8984/9/43/002/pdf

Muon spin rotation and relaxation in magnetic materials

The filled skutterudite CeOs4Sb12 and its nonmagnetic analogue LaOs4Sb12 have been synthesized in single-crystal form using the molten-metal-flux growth technique with Sb flux. Electrical resistivity measurements on CeOs4Sb12 indicate that it is a Kondo insulator with an energy gap of ΔE/kB~10 K. Lattice parameter and magnetic susceptibility measurements suggest that the Ce ions are trivalent in CeOs4Sb12. Specific heat and magnetization measurements reveal an enhanced value of the electronic specific heat coefficient γ~92 mJ mol-1 K-2 and Pauli susceptibility, reminiscent of a moderately heavy-fermion material.

https://iopscience.iop.org/article/10.1088/0953-8984/13/20/310/pdf

Kondo insulating behaviour in the filled skutterudite compound CeOs4Sb12

Encyclopedia of applied physics

Structural evolution of ball-milled ZnFe2O4

The formation of magnetic correlations in CeNiSn has been studied by muon spin rotation and relaxation (μSR) spectroscopy covering the temperature range from 250 K to 33 mK. Mainly a single crystalline sample was used. At high temperatures (≥ 2 K) a behaviour similar to that of a spin fluctuator like UAl2 is observed, meaning that over the whole temperature range the paramagnetic moments fluctuate extremely fast (≥ 31014 Hz). Below 1 K the material exhibits properties typical for a paramagnet moving towards magnetic order, but no transition into long-range order could be observed down to the lowest measured temperature. The dependences of muon spin relaxation rate and muon spin precession frequency on external field (applied parallel to the a-axis) are unusual and indicate the formation of extended spin correlations up to short-range order.

https://iopscience.iop.org/article/10.1209/0295-5075/19/7/014/pdf

A μSR Study of Magnetic Correlations in CeNiSn

Uranium moment collapse in magnetically diluted US

Magnetic order (including spin freezing) is absent down to ∼15 mK in CeNiSn due to the dominance of coherent spin fluctuations caused by the Kondo interaction. Partial replacement of Ni by Cu or Pt induces a highly disordered magnetic state. The critical concentration is much lower for Cu replacement (∼7%) than for Pt replacement (∼30%). Results of μSR and specific heat (for CeNi 1− x Cu x Sn) measurements near the critical concentration are presented. The possibility of a quantum critical point is discussed. A tentative phase diagram for the two parameters relevant for the onset of magnetism, the unit cell volume and the d electron density, is derived.

The onset of magnetism in CeNi1−xTxSn (T=Cu, Pt)

While the transition into the antiferromagnetic state in CePdSn proves to be of simple second order, the transition in CePtSn is of an unusual nature. About 1 K above TN the Ce moments enter a quasi-static state with the paramagnetic spins frozen at random orientations. In the antiferromagnetic states, well-developed shapr spin precession patterns are seen in both compounds. This feature is not easily reconciled with the incommensurate spin structures proposed by neutron diffraction measurements. Implications on spin structure resulting from the μSR data are discussed.

Magnetic properties of the Kondo metals CePtSn and CePdSn from μSR

Between 1 K and 33 mK CeNiSn behaves as a paramagnet approaching magnetic order, but no transition is observed. A strong reduction in the moment participating in the magnetic correlations is likely. The La-doped compounds give no magnetic response down to 1.5 K. CePtSn shows unusual spin freezing just above T N ≈8K and sharp transition into a more complex spin order around 5.2 K.

A. Kratzer

Papers

A μSR Study of Magnetic Correlations in CeNiSn

Uranium moment collapse in magnetically diluted US

The onset of magnetism in CeNi1−xTxSn (T=Cu, Pt)

Magnetic properties of the Kondo metals CePtSn and CePdSn from μSR

Magnetic behavior of CeTSn (T = Ni, Pt) from μSR and Mössbauer spectroscopy