Nuclear orientation and NMRON in rare earths

A +SR study of the rare earth antiferromagnet PrO2

“…where r µ is the position of the muon, µ i is the ordered magnetic moment of the i th Pr ion and ni (=(r µ − r i )/|r µ − r i |) is the unit vector from the muon to the Pr ion at site r i . The positive muon's position is usually in the vicinity of the electronegative O 2− ions [9]. The exact magnetic structure of PrO 2 is unknown and the available neutron data are consistent with either 1-k, 2-k or 3-k transverse type-I magnetic structures [10], together with a second component with twice the period along one axis [5].…”

Muon spin rotation studies of electronic excitations and magnetism in the vortex cores of superconductors

“…The external magnetic field H is applied transverse to the direction of the initial muon spin polarization P x (0), which defines the x-axis. In high-T c superconductors, the positive muon (µ + ) forms an ∼ 1 Å bond with an oxygen atom [9,10], but in general the muon will stop at an interstitial site in the sample. There the muon spin precesses about the local magnetic field B(r) in a plane perpendicular to the local field axis.…”

“…From observations of a weak temperature dependence for σ at low T it was concluded that the pairing state symmetry of high-T c superconductors is s-wave [17,18,19,20]. A linear scaling of T c with σ was also found (the so-called 'Uemura plot'), which has been interpreted via equation (10) to imply T c ∝ 1/λ 2 ab , which in turn is proportional to the superfluid density n s [21,22]. While the dependences of σ for newly discovered superconductors continue to be reported in the literature, the assumed relation σ ∝ 1/λ 2 ab is not precisely correct.…”

“…While the dependences of σ for newly discovered superconductors continue to be reported in the literature, the assumed relation σ ∝ 1/λ 2 ab is not precisely correct. One reason is that the use of equation (10) assumes one is aware of and understands all contributions to the measured value of σ. Brandt [13] has shown that for straight rigid vortex lines, σ is increased by both pinning-induced random displacements of the vortices from their ideal position in the FLL and thermal fluctuations of the vortex lines. On the other hand, the layered nature of the high-T c superconductors means that the vortices can be highly flexible.…”

Magnetic ordering and dynamics in the XY pyrochlore antiferromagnet: a muon-spin relaxation study of Er2Ti2O7and Er2Sn2O7

“…In the cubic pyrochlore lattice (space group = F3dm; standard setting), the oxygen anions are located at two crystallographic positions: 8a and 48f, and a calculation of the local dipolar fields at these sites in the ψ 2 spin structure with µ (Er 3+ ) = 3.01 µ B shows that the field does indeed vanish at the 8a position (and reaches a value of ∼2600 G at 48f). However, muons do not stop precisely at the oxygen positions but are usually considered to reside at a distance of 1 Å away from them [16], in which case the internal field rises up to values of ∼5000-17 000 G along the main crystallographic directions from the 8a position. For the 48f site, on the other hand, the field adopts a minimum value of ∼600 G about 1 Å away along 100 .…”