Funktionen,deren Logarithmus darstellbar ist als Differenz subharmonischer Funktionen

Ohne Zusammenfassung Dieser Artikel ist ein Auszug der Dissertation des Verfassers.     

Can one observe by μ SR the transition from uncorrelated to correlated spin fluctuations? Example: Nd1.4Ce0.2Sr0.4CuO4-\delta

μSR‐measurements in ZF and LF on Nd_1.4Ce_0.2Sr_0.4CuO_4-\delta show a sharp increase of the depolarisation rate (\lambda) below \approx\,2K. This increase can be explained by the transition from uncorrelated to correlated spin fluctuations, which is in agreement with results obtained by neutron scattering. This revised version was published online in August 2006 with corrections to the Cover Date.     

μSR studies of the low‐temperature magnetism in a valence‐fluctuation compound Sm3Se4

The spin relaxation of Mu was measured in mixtures of CO and Ar at pressures up to 270 atm and at various magnetic fields. The relaxation rate increased with magnetic field in the way expected for electron spin‐exchange processes, though the effect declined at high pressures. We describe the results in terms of spin relaxation of Mu‐formyl radicals, MuCO, which break up to give depolarized Mu at low pressures, but are increasingly stabilized at higher pressures. This revised version was published online in August 2006 with corrections to the Cover Date.     

Measurement of the field dependence (Knight shift) of the hyperfine field at a positive muon in ferromagnetic nickel

The dependence of the hyperfine field at an interstitial positive muon in ferromagnetic field has been measured at room temperature yielding a Knight Shift constant K = 0.0025 (3). This Knight shift is interpreted in terms of the Pauli spin paramagnetism of s-p band electrons.     

A comparative study of the magnetic heavy-electron materials U2Zn17 and UCu5 by μ+SR

A systematic μ⁺SR study of the magnetic heavy-electron systems U₂Zn₁₇ and UCu₅ in the paramagnetic and in the magnetically ordered state is presented. In both systems the antiferromagnetic nature of the low-temperature phase could be at least partially confirmed, but the muon reveals significant differences with regard to the phase transition itself. UCu₅ behaves like a model-antiferromagnet showing a drastic increase of the relaxation rate both below and above T_N, two spontaneous frequencies in the ordered phase, and a Knight shift above T_N which scales with the bulk susceptibility. In contrast U₂Zn₁₇ shows a loss of μ⁺ asymmetry by 20% below T_N, which is independent of the external field but can be quenched in sufficiently strong longitudinal fields. No scaling of the Knight shift and the susceptibility was observed and no critical increase of the relaxation rate λ. Most astonishing is the strong and nonlinear field dependence of λ above and below T_N in both compounds. The absence of longitudinal relaxation demonstrates the static origin of λ.