Temperature dependence of nuclear spin-lattice relaxation in the heavy-fermion superconducting state

Some features of the experimental data on nuclear spin relaxation time T₁ in the heavy-fermion superconducting state can be explained by taking into account the effect of the electron Zeeman energy. It is found that at intermediate temperatures the usual quasiparticle spin-flip scattering dominates, while at very low temperatures a new process, pair creation (annihilation), dominates and gives T^-1₁ ∝ T.     

Temperature dependence of self-reversal of magnetization of nickel

The temperature dependence of the self-reversal of magnetization of polycrystalline nickel wire at temperatures from room temperature to the Curie point is examined and interpreted. The critical field for self-reversal and the reversed magnetization decrease steadily towards the Curie point and are affected by tension and the prehistory of the specimen.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 52–55, January, 1973.     

Temperature dependence of surface magnetization in local-moment systems

We present a theory to study the temperature-dependent behavior of surface magnetization in a ferromagnetic semi-infinite crystal. Our approach is based on the single-site approximation for the s-f model. The effect of the semi-infinite nature of the crystal is taken into account by a localized perturbation method. Using the mean-field theory for the layer-dependent magnetization, the local density of states and the electron-spin polarization are investigated at different temperatures for ordinary and surface transition cases. The results show that the surface magnetic properties may differ strongly from those in the bulk and the coupling constant of atoms plays a decisive role in the degree of spin polarization. In particular, for the case in which the exchange coupling constant on the surface and between atoms in the first and second layer is higher than the corresponding in the bulk, an enhancement of surface Curie temperature and hence the spin polarization can be obtained.     

Temperature dependence of magnetization in nanocrystalline FeCoZr alloy

The temperature dependence of magnetization of a nanocrystalline Fe₆₀Co₃₀Zr₁₀ alloy annealed at various temperatures to varying crystal sizes was investigated down to 5 K in the field range up to 5 T. The fitting procedure gave T^3/2 as the leading term irrespective of the crystal size. We suggest that the increase of the coefficient by this term for smaller crystals may be connected to an increased relative volume of their surface.     

Temperature and frequency dependence of the nuclear relaxation rate in Qn(TCNQ)2

The magnitude, frequency dependence and temperature dependence of the proton relaxation rates in Qn(TCNQ)₂ are explained in terms of a theory which treats the short wavelength response as coherent and one-dimensional, while the long wavelength response is dominated by anisotropic (intrachain vs interchain) diffusion. The diffusive character of the response near q = 0 is consistent with recent attempts to understand the electronic properties of Qn(TCNQ)₂ in terms of weak localization of states in one-dimension. Analysis of the data leads to the conclusion that the effective screened Coulomb interaction is relatively weak.     

Non-exponential relaxation of nuclear magnetization in solid ortho-para hydrogen mixtures

We report calculations of the decay of the nuclear magnetization of different isochromats in the NMR absorption spectrum of solid mixtures of ortho-para hydrogen. The calculated decays show significant departures from exponential recovery and are in good overall agreement with experimental results reported elsewhere. A slowly component, characteristic of the quadrupolar glass phase is predicted at long times.     

Temperature dependence of the magnetization of canted spin structures

Numerous studies of the low-temperature saturation magnetization of ferrimagnetic nanoparticles and diamagnetically substituted ferrites have shown an anomalous temperature dependence. It has been suggested that this is related to freezing of canted magnetic structures. We present models for the temperature dependence of the magnetization of a simple canted spin structure in which relaxation can take place at finite temperatures between spin configurations with different canting angles. We show that the saturation magnetization may either decrease or increase with decreasing temperature, depending on the ratio of the exchange coupling constants. This is in agreement with experimental observations.     

Temperature dependence of nuclear surface properties

Thermal properties of nuclear surface are investigated in a semi-infinite medium. Explicit analytical expressions are given for the temperature dependence of surface thickness, surface energy and surface free energy. In this model the temperature effects depend critically on the nuclear incompressibility and on the shape of the effective mass at the surface. To illustrate the relevance of these effects we made an estimate of the temperature dependence of the fission barrier height.     

Temperature dependence of electron magnetic resonance and magnetization in NiO nanorods

For NiO nanorods of 5 nm diameter prepared by sol-gel technique, variations of the magnetization M with temperature T (5-370 K) and magnetic field H up to 55 kOe are reported. Also, temperature variations of the EMR (electron magnetic resonance) parameters (intensity I₀, linewidth ΔH and resonance field H_r) of an observed line due to uncompensated spins are followed for The M vs. H and T variations yield a blocking above which the data fits modified Langevin function with magnetic moment μ_p?1240 μ_B/particle. For the EMR line, I₀ decreases rapidly for T<T_B, and the line broadens and shifts to lower H with lowering T, following the lineshift δH_r=(ΔH)ⁿ with n?2.8. This is close to the value of n=3 expected for randomly oriented particles.     

Temperature dependence of the saturation magnetization of ion-implanted YIG films

The temperature dependence of the saturation magnetization of a series of ionimplanted YIG films is presented. The films were implanted with neon ions at an energy of 450 keV; the dose ranged from 2 to 5*10¹⁴ ions/cm². The experimental data can be described by the molecular field theory showing that the ion-implanted part of the film can be approximated as consisting of two regions each having their own magnetization and Curie temperature. The values of these magnetic parameters vary as a function of dose and differ strongly from the values for pure YIG.     

Temperature dependence of proton relaxation times in vitro

Accurate measurement of tissue relaxation characteristics is dependent on many factors, including field strength and temperature. The purpose of this study was to evaluate the relationship between sample temperature, viscosity and proton spin-lattice relaxation time (T1) and spin-spin relaxation time (T2). A review of two basic models of relaxation the simple molecular motion model and the fast exchange two state model is given with reference to their thermal dependencies. The temperature dependence for both T1 and T2 was studied on a 0.15 Tesla whole body magnetic resonance imager. Thirteen samples comprising both simple and complex materials were investigated by using a standard spin-echo (SE) technique and a modified Carr-Purcell-Meiboom-Gill (CPMG) multi-echo sequence. A simple linear relationship between T1 and temperature was observed for all samples over the range of 20 degrees C to 50 degrees C. There is an inverse relationship between viscosity and T1 and T2. A quantity called the temperature dependence coefficient (TDC) is introduced and defined as the percent rate of change of the proton relaxation time referenced to a specific temperature. The large TDC found for T1 values, e.g. 2.37%/degrees C for CuSO4 solutions and 3.59%/degrees C for light vegetable oils at 22 degrees C, indicates that a temperature correction should be made when comparing in-vivo and in-vitro T1 times. The T2 temperature dependence is relatively small.     

Temperature dependence of magnetization of pyrrhotines in a metastable phase state

Magnetic properties of iron sulfides in a metastable phase state were investigated. During heating of iron sulfides of the composition Fe_0.901S up to 150°C a magnetization increase was observed. It was shown that the observed effect is not the known transition and that it results from the redistribution of vacancies of iron ions in basal planes of the crystal structure of the NiAs type. A theoretical model was proposed which explains qualitatively this effect.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 56–61, April, 1989.     

Temperature dependence of relaxation processes in network polymeric systems

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 48, No. 1, pp. 110–114, January, 1988.     

Temperature dependence of Pt(111) surface relaxation

A careful investigation of the Pt(111) surface has been carried out, using the MeV heliumscattering technique. The anomalously large surface relaxation effect reported previously has been identified as an experimental artifact resulting from an unexpectedly large surface damage effect at low temperature. Optimum conditions have been established for minimizing the main experimental sources of error: background subtraction, radiation damage, and deviations from the Rutherford scattering law. Using these optimum conditions, a series of scattering measurements has been made over the temperature range 40–300 K. At all temperatures, we observe a significant anisotropy in the 〈111〉 angular scans, indicating an outward relaxation of the Pt(111) surface plane. By comparing this observed anisotropy with a set of Monte Carlo simulations, a value of 0.03 ? 0.01 Å (i.e. 1.3 ? 0.4%) is obtained for the surface relaxation. The temperature dependence of the surface peak also indicates that the enhanced vibrational amplitude of the surface atoms is not nearly as large as had been derived previously from high-temperature LEED studies.     

Temperature and spatial dependence of the magnetization near a surface of a ferromagnet

The temperature and spatial dependence of the magnetization in a semi-infinite, single tight-binding band model ferromagnet is calculated. It is assumed that the spatial dependence of the magnetization arises primarily because of the downward shift of the ‘atomic’ energy level in the surface layer. This shift was found to occur in Ni in a previous calculation. The effects of the surface are approximated by considering a plane of defects in an otherwise translationally invariant metal. The surface layer is furthermore assumed to be paramagnetic as was previously suggested to be the case for Ni. It is demonstrated that the range of the magnetic disturbance arising from the surface increases with temperature and that the deviation in the magnetization of a given layer from the bulk magnetization is a damped oscillatory function of the distance of the layer from the surface. while the present theory assumes a highly over simplified model for the band structure and it is, therefore, not reasonable to apply these calculations directly to real metals, the results found here are qualitatively consistent with experiments on Ni.