Phys. Rev. B 102, 054426 (2020) We present a systematic 57Fe-Moessbauer study on highly diluted Fe centers in
Li2(Li1-xFex)N single-crystals as a function of temperature and magnetic field
applied ...transverse and longitudinal with respect to the single-ion anisotropy
axis. Below 30 K the Fe centers exhibit a giant magnetic hyperfine field of E_A
= 70.25(2)T parallel to the axis of strongest electric field gradient Vzz =
-154.0(1) V/A2. Fluctuations of the magnetic hyperfine field are observed
between 50K and 300K and described by the Blume two-level relaxation model.
From the temperature dependence of the uctuation rate an Orbach spin-lattice
relaxation process is deduced. An Arrhenius analysis yields a single thermal
activation barrier of E_A = 570(6)K and an attempt frequency nu_0 = 309(10)
GHz. Moessbauer spectroscopy studies with applied transverse magnetic fields up
to 5T reveal a large increase of the uctuation rate by more than one order of
magnitude. In longitudinal magnetic fields a splitting of the uctuation rate
into two branches is observed consistent with a Zeeman induced modifcation of
the energy levels. The experimental observations are qualitatively reproduced
by a single-ion effective spin Hamiltonian analysis assuming a Fe1+ d7 charge
state with unquenched orbital moment and a J = 7=2 ground state. It is
demonstrated that a weak axial single-ion anisotropy D of the order of a few
Kelvin can cause a two orders of magnitude larger energy barrier for
longitudinal spin fluctuations.
We report ultrasound studies of spin-lattice and single-ion effects in the spin-ice materials Dy sub(2) Ti sub(2) O sub(7) (DTO) and Ho sub(2) Ti sub(2) O sub(7) (HTO) across a broad field range up ...to 60 T, covering phase transformations, interactions with low-energy magnetic excitations, and single-ion effects. In particular, a sharp dip observed in the sound attenuation in DTO at the gas-liquid transition of the magnetic monopoles is explained based on an approach involving negative relaxation processes. Furthermore, quasiperiodic peaks in the acoustic properties of DTO due to nonequilibrium processes are found to be strongly affected by macroscopic thermal-coupling conditions: the thermal runaway observed in previous studies in DTO can be suppressed altogether by immersing the sample in liquid helium. Crystal-electric-field effects having a higher energy scale lead to a renormalization of the sound velocity and sound attenuation at very high magnetic fields. We analyze our observations using an approach based on an analysis of exchange-striction couplings and single-ion effects.
We present a comparative analysis of the layout-aware fault injection simulation results for Direct Memory Access (DMA) controllers with local, distributed, global and block Triple Modular Redundancy ...(TMR). The applied technique is also presented.
Phys. Rev. B (2023) Spin systems with honeycomb structures have recently attracted a great deal
of attention in connection with the Kitaev quantum spin liquid state (QSL)
predicted theoretically. One ...possible Kitaev QSL candidate is
Na$_2$Co$_2$TeO$_6$ realizing a honeycomb lattice of pseudo-spin-1/2.
Field-dependent single-crystal neutron diffraction technique allows us to
determine the microscopic spin-spin correlations across the field induced phase
transitions for H//a and H//a* in plane field directions. Our results reveal
phase transitions, initially to a canted zigzag antiferromagnetic state at
approximately 60 kOe, followed by a possible transition to a partially
polarized state over the range of 90-120 kOe, and finally to a field-induced
fully polarized state above 120 kOe. We observe distinct field dependencies of
the magnetic peak intensities for H//a and H//a*. In addition, low-temperature
electron spin resonance in magnetic fields H//c yields a complete softening for
one of the antiferromagnetic resonances at ~ 40 kOe, revealing a field-induced
phase transition. The present work, thus, provides new insights into the field
evolution of the important Kitaev-Heisenberg spin system Na$_2$Co$_2$TeO$_6$.
EPR experiments were performed on powder samples of the quasi-one-dimensional
S = 1 spin systems NENC and TMNIN in the frequency range 55–400 GHz in magnetic fields up to 14 T. In both materials ...broad and asymmetric line shapes were observed pointing to a strong planar anisotropy. We interpreted the measured line shapes using a single-ion Hamiltonian. Transition matrix elements and occupation number of energy levels are taken into account in these calculations. In this way we obtain a good estimate for both the planar anisotropy
D and the in-plane anisotropy
E.
We propose and demonstrate a novel technique, which we term bifocal optical coherence refractometry, for the rapid determination of the refractive index of a turbid medium. The technique is based on ...the simultaneous creation of two closely spaced confocal gates in a sample. The optical path-length difference between the gates is measured by means of low-coherence interferometry and used to determine the refractive index. We present experimental results for the refractive indices of milk solutions and of human skin in vivo. As the axial scan rate determines the acquisition time, which is potentially of the order of tens of milliseconds, the technique has potential for in vivo refractive-index measurements of turbid biological media under dynamic conditions.
We report on the measurement of the magnetic susceptibility and of ESR transitions in the garnet substance Tb\(_3\)Ga\(_5\)O\(_{12}\) (TGG). The results are compared with a calculation in the ...framework of crystal field theory for the orthorhombic surroundings of the six inequivalent Tb ions of TGG. We also present a calculation of the magnetization for the three main crystal directions.
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