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Nd2Hf2O7, belonging to the family of geometrically frustrated cubic rare earth pyrochlore oxides, was recently identified to order antiferromagnetically below TN 0.55 K with an all in all out arrangement of Nd3 moments, however, with a much reduced ordered state moment. Herein, we investigate the spin dynamics and crystal field states of Nd2Hf2O7 using muon spin relaxation muSR and inelastic neutron scattering INS measurements. Our muSR study confirms the long range magnetic ordering and shows evidence for coexisting persistent dynamic spin fluctuations deep inside the ordered state down to 42 mK. The INS data show the crystal electric field CEF excitations due to the transitions both within the ground state multiplet and to the first excited state multiplet. The INS data are analyzed by a model based on CEF and crystal field states are determined. Strong Ising type anisotropy is inferred from the ground state wave function. The CEF parameters indicate the CEF split Kramers doublet ground state of Nd3 to be consistent with the dipolar octupolar character

We have investigated the noncentrosymmetric tetragonal heavy fermion compound CeAuAl3 using muon spin rotation (µSR), neutron diffraction (ND), and inelastic neutron scattering (INS) measurements. We have also revisited the magnetic, transport, and thermal properties. The magnetic susceptibility reveals an antiferromagnetic transition at 1.1 K with, possibly, another magnetic transition near 0.18 K. The heat capacity shows a sharp ¿-type anomaly at 1.1 K in zero field, which broadens and moves to a higher temperature in an applied magnetic field. Our zero-field µSR and ND measurements confirm the existence of a long-range magnetic ground state below 1.2 K. Further, the ND study reveals an incommensurate magnetic order with a magnetic propagation vector k=(0, 0, 0.52(1)) and a spiral structure of Ce moments coupled ferromagnetically within the ab plane. Our INS study reveals the presence of two well-defined crystal electric field (CEF) excitations at 5.1 and 24.6 meV in the paramagnetic phase of CeAuAl3 that can be explained on the basis of the CEF theory and the Kramer''s theorem for a Ce ion having a 4f1 electronic state. Furthermore, low energy quasielastic excitations show a Gaussian line shape below 30 K compared to a Lorentzian line shape above 30 K, indicating a slowdown of spin fluctuations below 30 K. We have estimated a Kondo temperature of TK=3.5K from the quasielastic linewidth, which is in good agreement with that estimated from the heat capacity. This study also indicates the absence of any CEF-phonon coupling unlike that observed in isostructural CeCuAl3 The CEF parameters, energy level scheme, and their wave functions obtained from the analysis of INS data explain satisfactorily the single crystal susceptibility in the presence of two-ion anisotropic exchange interaction in CeAuAl3.

Results of muon spin relaxation amp; 956;SR and neutron powder diffraction measurements on a reentrant superconductor Eu Fe0.86Ir0.14 2As2 are presented. Eu Fe0.86Ir0.14 2As2 exhibits superconductivity at Tc on amp; 8776; 22.5 K competing with long range ordered Eu 2 moments below amp; 8776;18 K. A reentrant behavior manifested by nonzero resistivity in the temperature range 10 17.5 K results from an exquisite competition between the superconductivity and magnetic order. The zero field amp; 956;SR data confirm the long range magnetic ordering below TEu 18.7 2 K. The transition temperature is found to increase with increasing magnetic field in longitudinal field amp; 956;SR which along with the neutron diffraction results, suggests the transition to be ferromagnetic. The neutron diffraction data reveal a clear presence of magnetic Bragg peaks below TEu which could be indexed with propagation vector k 0, 0, 0 , confirming a long range magnetic ordering in agreement with amp; 956;SR data. Our analysis of the magnetic structure reveals an ordered magnetic moment of 6.29 5 amp; 956;B at 1.8 K on the Eu atoms and they form a ferromagnetic structure with moments aligned along the c axis. No change in the magnetic structure is observed in the reentrant or superconducting phases and the magnetic structure remains same for 1.8 K lt; T lt; TEu. No clear evidence of structural transition or Fe moment ordering was found

We have investigated the superconducting state of the non-centrosymmetric compound Re\(_6\)Zr using magnetization, heat capacity, and muon-spin relaxation/rotation (\(\mu\)SR) measurements. Re\(_6\)Zr has a superconducting transition temperature, T\(_c\) = 6.75±0.05 K. Transverse-field \(\mu\)SR experiments, used to probe the superfluid density, suggest an \(s\)-wave character for the superconducting gap. However, zero and longitudinal-field \(\mu\)SR data reveal the presence of spontaneous static magnetic fields below \(T\)\(_c\) indicating that time-reversal symmetry is broken in the superconducting state and an unconventional pairing mechanism. An analysis of the pairing symmetries identifies the ground states compatible with time-reversal symmetry breaking.

Low-temperature magnetic susceptibility and heat-capacity measurements on nanoparticles (d? 2.6 nm) of the antiferromagnetic compounds DyPO4 (TN=3.4 K) and GdPO4 (TN=0.77 K) provide clear demonstrations of finite-size effects, which limit the divergence of the magnetic correlation lengths, thereby suppressing the bulk long-range magnetic ordering transitions. Instead, the incomplete antiferromagnetic order inside the particles leads to the formation of net magnetic moments on the particles. For the nanoparticles of Ising-type DyPO4 superparamagnetic blocking is found in the ac susceptibility at ?1 K, those of the XY-type GdPO4 analog show a dipolar spin-glass transition at ?0.2 K. Monte Carlo simulations for the magnetic heat capacities of both bulk and nanoparticle samples are in agreement with the experimental data. Strong size effects are also apparent in the Dy3+ and Gd3+ spin dynamics, which were studied by zero-field muon spin rotation (?SR) and high-field 31P-nuclear magnetic resonance (31P-NMR) nuclear relaxation measurements. The freezing transitions observed in the ac susceptibility of the nanoparticles also appear as peaks in the temperature dependence of the zero-field ?SR rates, but at slightly higher temperatures, as to be expected from the higher frequency of the muon probe. For both bulk and nanoparticles of GdPO4, the muon and 31P-NMR rates are for T?5 K dominated by exchange-narrowed hyperfine broadening arising from the electron spin-spin interactions inside the particles. The dipolar hyperfine interactions acting on the muons and the 31P are, however, much reduced in the nanoparticles. For the DyPO4 analogs the high-temperature rates appear to be fully determined by electron spin-lattice relaxation processes.