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We report on the structures of the magnetic phases of CeRu2Ge2 and their evolution in the series Ce(Ru1-xFex)2Ge2. The crossover behavior between the ferromagnetic ground state of CeRu2Ge2 to the paramagnetic ground state of CeFe2Ge2 is compared to the behavior in the series CeRu2(Ge1-xSix)2. A profound difference is observed between these two series, which is in contradiction to the uniform behavior predicted by the Doniach-necklace model. [ABSTRACT FROM AUTHOR]

Below 30 K, magnetic order was found in La1.85-x Nd_x Sr0.15 CuO_4 with x ranging between 0.30 and 0.60. This order occurs in the low temperature tetragonal phase. Below 5 K, the interaction of Nd and Cu moments modifies the magnetic order in the Cu–O planes leading to an increase of the muon spin rotation frequency and the transverse damping rate. Even down to 0.1 K, considerable spin dynamics is observable. [ABSTRACT FROM AUTHOR]

The spin dynamics in the reentrant spin glass ( Fe0.65 Ni0.35)1-x Mn_x has been studied by zero, longitudinal and transverse field μSR. In the ferromagnetic reentrant and pure spin glass regimes (x\leqslant 0.175), zero field experiments reveal a stretched exponential muon relaxation with a universal behaviour of the dynamic exponent \beta above the spin glass transition. There are no qualitative differences between the ferromagnetic and paramagnetic phases. In transversal field μSR experiments the divergence of the relaxation rate close to the spin glass transition is suppressed for manganese doping up to x=0.113 but enhanced for slightly higher doping (x\geqslant 0.12). We understand this behaviour as a crossover from an itinerant to a more localized state of the 3d electron system. This is also supported by the fact that in the highly doped regime with dominant antiferromagnetic interactions the muon relaxation rate diverges above the antiferromagnetic transition temperature. [ABSTRACT FROM AUTHOR]

μSR experiments on NdCu2 give evidence for short range order below 25\ K above TN=6.5\ K. No signal was detected between 16\ K and 1.2\ K where neutron scattering reveals an incommensurate spin structure. Below 1.2\ K the μSR signal is recovered and shows a rotation with 22 MHz. This is interpreted with a squaring up of Nd spins accompanied by a decrease of magnon excitations which is reflected in a decrease of damping of the muon signal. [ABSTRACT FROM AUTHOR]

The magnetic correlations in Nd2-yCeyCuO4 have been studied by zero and longitudinal field μSR. Nd1.8Ce0.2CuO4 reveals a saturation of the muon relaxation rate below 0.5 K. Even down to 70 mK LF spectra evidence spin fluctuations in the dynamic regime with a rate of \sim 109 s-1 excluding long range magnetic order or spin glass freezing. The average Nd moment is estimated to be \approx 0.2\muB, i.e., strongly reduced from the value determined for the ground state Kramers doublet of Nd2CuO4. Extending former μSR measurements on Nd2CuO4, a gradual enhancement of the internal field has been detected below 10 K which is accompanied by an increase of the relaxation rate. These results are attributed to the development of ordered Nd moments. [ABSTRACT FROM AUTHOR]

Zero and longitudinal field μSR have been used to examine the singlet ground state magnetism of the diluted magnetic semiconductor Hg1-xFexSe. For x\geq 0.05\ μSR experiments indicate spin glass behaviour which is limited to sample regions with locally enhanced Fe2+ content. Longitudinal field spectra in the glassy state reveal a static local field \sim 50 mT due to induced moments of Fe2+. These are proposed to originate from a distribution of bound magnetic polaron energies. [ABSTRACT FROM AUTHOR]