Temperature Dependence Of Electric Field Gradient Research Articles

Anomalous variation of electric field gradient in [formula omitted

Variation of electric field gradient (EFG) at 181Ta occupying substitutional sites in α ‐ Ti matrix has been studied in the temperature interval from 10 to 300 K using time differential perturbed angular correlation spectroscopy. Among the main sources of EFG such as conduction electrons and lattice ions, the present study shows that in α ‐ Ti , the temperature dependence of EFG is predominantly due to conduction electrons. The variation of EFG could not be fitted with either as the linear dependence of temperature ( T) or T 3/2 over the whole temperature interval 10–300 K. Existence of two different slopes with a change of slope occurring around 150 K is observed while the EFG is fitted with T or T 3/2. The above change of slopes of EFG in α ‐ Ti , which is understood to be due to a slight modification in conduction electron–phonon interactions based on this work, is possibly caused by the electronic topological transitions below 150 K as has been reported.

Temperature dependence of electric-field gradients at isolated Se adatoms on (001) and (111) surfaces and derived adatom distances

Increasing electric-field gradients (EFG) with increasing temperature were observed at isolated Se adatoms on Ni(111), Pd(111), and Co(0001) surfaces applying perturbed angular correlation spectroscopy. This is in contrast to EFG's at probes on surfaces w

Critical behavior of electric field gradient in MnSi studied by muon level-crossing resonance

The electric quadrupole interaction of55Mn nuclei was studied in the weakly ferromagnetic system MnSi using muon level-crossing resonance (μLCR) technique. The temperature dependence of the electric field gradient (EFG) shows a critical behavior near the ferromagnetic transition temperature, indicating that the EFG due to the conduction electron is strongly correlated with the magnetic susceptibility in the itinerant electron magnetism. The temperature dependence of EFG is in reasonable agreement with the self-consistent renormalization theory developed by Moriya and coworkers.

Current Status of Theory of Nuclear Quadrupole Interaction in Metallic Systems

This paper deals with the current status of understanding of the factors that determine the origin of nuclear quadrupole interactions in metallic systems. The major emphasis is on pure metals in which there is currently better understanding of the origin of the electric field gradient (EFG) at the nuclear sites. The procedures for the determination of the electron densities that lead to the electronic contributions to the EFG’s is discussed as well as the quantitative procedures for incorporation of antishielding effects. The nature of agreement between theory and experiment is examined by considering the hexagonal close packed metals beryllium, magnesium, zinc and cadmium. The sensitiveness of the calculated EFG to the procedure used for obtaining electron densities is discussed in beryllium using orthogonalized plane wave and augmented plane wave procedures. The nature of agreement between theory and experiment currently attainable for semi-metals and semiconductors is discussed. The bearing of some of the results in these latter systems by procedures dealing with clusters of atoms to simulate the infinite solid on the future of such procedures for imperfect systems and surfaces is commented upon. A brief discussion is presented about the various possible contributors to the temperature dependence of EFG’s in pure metals and comparison is made between theory and experiment for zinc and cadmium. The factors that can contribute to the EFG’s in imperfect metallic systems, including alloys, at both host and impurity nuclei are discussed, and some of these factors are illustrated by considering two examples of these systems, EFG ’s at host Al and Cu nuclei due to mu mesons introduced in the metal and at impurity nuclei in alloys involving cadmium metal host. The concluding section discusses directions in which further efforts are needed to improve our theoretical understanding of both pure metals and imperfect metallic systems.

Temperature dependence of the electric quadrupole interaction in PbHfO 3

The temperature dependence of the Electric Field Gradient (EFG) in PbHfO 3 was studied in the temperature range 25–225°C by the Differential Perturbed Angular Correlation method. In the two anti-ferroelectric phases below 215°C, not too close to either transition temperature, the EFG decreases as the temperature increases toward T c . Just above T c an abrupt rise of EFG was observed indicating a critically behaving contribution to EFG. The results are interpreted in terms of a model based on the local static as well as time-dependent changes of the electric environment, at a lattice site. In accord with the predictions of this model the results exhibit qualitatively the P 2 s temperature dependence of EFG far from T c , where P s is the sub-lattice polarization, while in close proximity to T c the dominant contribution to EFG is due to the susceptibility X q connected with the soft-mode fluctuations. The derived critical exponents are in agreement with previous experimental results on related compounds and with theoretical predictions. A hitherto unobserved additional component of V zz was established, behaving critically at the antiferro-paraelectric transition at 215°C. This new component is interpreted to originate in local fluctuations connected with the central mode.

Static and dynamic aspects of perturbed angular correlation measurements in perovskite crystals

Abstract The static and dynamic aspects of the Electric Field Gradient (EFG) in ionic perovskite (anti-) ferroelectric crystals have been studied with particular emphasis on the Perturbed Angular Correlation method. We analyze the effect of the lattice fluctuations on the temperature behavior of the EFG. The proper averaging procedure of the perturbation function is outlined. This results in a simple relationship between the electric (sub-) lattice susceptibility and the measured EFG, predicting a critical behavior of EFG on approaching T c . In addition to this dynamical effect we show that well below T c , the temperature dependence of EFG is dominated by P s 2 , the square of the spontaneous polarization of the (sub-) lattice. These predictions are shown to be in qualitative agreement with published experimental data.

Study on the Ferroelectric Phase Transition in RbDSO4by NMR II. Deuteron Magnetic in Ferroelectric Phase

The principal coordinate systems of electric field gradient (EFG) at deuteron sites in hydrogen bonds are obtained at -120°C by means of Volkoff method. The shift in angle of 10 degrees is found in the orientation of the principal z axis of EFG at two of four inequivalent sites, and about 3 degrees at the other two sites. These shifts are attributable to the rotational displacement of SO 4 ions. The temperature dependence of the resonance line separation is measured in the ferroelectric phase with the magnetic field parallel to the crystalline a axis. It is found that this temperature dependence, that is, the temperature dependence of EFG is proportional to the spontaneous polarization obtained in the present study by the pyroelectric method. In the limited temperature range, from -30 to -100°C, the separation of resonance lines and the spontaneous polarization depend on temperature as ( T c - T ) β , with β of 0.33.