Positive Muons as Local Probes in Paramagnetic Rare Earth Systems

In recent years a new research method has been developed in solid state physics which is based on the asymmetry of muon decay1. A positive muon at rest decays after a mean lifetime of 2.2 μsec into a positron and two neutrinos, the positron being emitted preferentially in the direction of the muon spin. Hence if spin polarized muons are implanted in a solid, the time evolution of the muon spin polarization can be determined by a measurement of the angular distribution of the positrons. In an external magnetic field transverse to the initial spin direction of the muon one can study the muon spin precession frequency, which is determined by the actual field at the muon, and τ2-relaxation effe…

Anomalous Muon Knight Shift Behavior in a Cd Single Crystal

For the positive muon implanted in a metal the precession frequency shift due to hyperfine fields can be measured with high precision. This provides means to obtain information about the local electronic structure of a hydrogen like impurity in any metal in the indefinitely dilute impurity concentration. Ref. 1 gives a summary of the muon Knight shift (KS) investigations in 18 nontransition (simple) metals and some transition metals and discusses the results in the context of the electronic structure of hydrogen in metals.

Muon Knight shift studies of the valence transition in Ce0�74Th0�26

Muon Knight shift at a structural defect in zinc crystals

The interaction of a light hydrogen isotope with a structural defect is traced for the first time by means of the temperature dependence of the muon Knight shiftKμ in the hcp metal Zn. A surprising result is the huge and negativeKμ (−520 ppm) at the defect site, probably a multivacancy cluster.

Crystal Field Excitations in CeAgl−xInx Compounds

The substitution of the monovalent Ag for the trivalent In in LaAgl−xInx and CeAgl−xInx offers the possibility of influencing the conduction electron system in these compounds. The strong dependence of the spin susceptibility of La-systems on the In-concentration1 was interpreted by band calculations which suggest that the Fermi level is pushed into a region of a high 5d-eg-band density of states2. Furthermore, CeAgl−xInx is one of the rare 4f systems where a structural phase transition (from cubic to tetragonal) occurs prior to magnetic ordering. The ferromagnetic Curie temperature TC is roughly independent of x whereas the structural transition temperature Ts rises from 15 K for CeAg to a…

Oxide growth and tunneling characteristics of Sn-SnO x -Sn junctions

Sn—SnOx—Sn tunneling junctions were prepared by thermal oxidation of vacuum deposited Sn-films. The thickness growth of the oxide was followed by ellipsometric measurements. From logarithmic conductivity measurements the barrier heights were determined. The tunneling characteristic could be well described by the two-band-tunneling model using a value of 0.14 for the ratio of the effective masses in the oxide and the metal.

Muon Knight shift studies in single crystals of Zn and Cd

Recently f i r s t resul ts have been reported on the muon Knight s h i f t in high pu r i t y (6N) spherical s ingle crys ta ls of Cd and Zn [ l ] . These measurements, using a stroboscopic ~SR-technique [2 ] , are extensions of e a r l i e r ~+ Knight s h i f t measurements in nontrans i t ion metals [3 ,4] in which the pos i t i ve muon is used as a "hydrogen" subs t i tu te in the study of i t s local e lec t ron ic s t ructure in a metal environment. Since the s o l u b i l i t y of hydrogen in these metals is general ly very small , no proton-NMR measurements have ever been performed in th is class of metals. To the extent that the mass d i f ference between the proton and the muon is…

Muon Knight-shift measurements in CeSn3and some isostructural rare-earth compounds

Muon spin rotation studies in single crystals of Zn and Cd

Anisotropic muon Knight shift in the HCP single crystals of Cd, Zn and Be

In single crystal samples of Zn, Cd and Be (hcp structure) stroboscopicμSR measurements successfully revealed anisotropies in the muon Knight shift (Kμ). An anisotropic Kμ can provide information on the amount of non s-electrons screening the charge of the muon implanted in these metals as a light hydrogen isotope. In Cd, the anisotropic part depends strongly on the temperature and shows a change in sign at roughly 110 K. In Zn, the anisotropic part below 10 K turns out to comprise 4th order contributions in the direction cosines of the external field. This can be understood on the basis of an anisotropicg-factor of the conduction electrons or spin-orbit coupling, respectively.