Anisotropic chemical shift of nuclear magnetic resonance in single crystals of tellurium and selenium

Abstract

The anisotropies of the chemical shifts in tellurium and selenium are analysed theoretically. It is shown that the second order paramagnetic chemical shift gives the main contribution t o the anisotropies. The anisotropy of the chemical shift is calculated assuming molecular wave functions for the valence electrons derived on the basis of Reitz's band calculation and good agreement is obtained with the observed anisotropy for tellurium. It is found in the analysis that there exists about 2% mixing of the bonding and the antibonding orbitals in the upper valence band states of tellurium. More elaborate calculations, however, seem to be necessary to explain the anisotropic chemical shift in selenium.Die Anisotropien der chemiscben Verschiebung in Tellur nnd Selen werden theoretisch analysiert. Es zeigt sich, daB hauptsiichlich die paramagnetische chemische Verschiebung zweiter Ordnung zur Anisotropie beitriigt. Die Anisotropie der chemischen Verschiebung wird mit den auf Grund der Bandberechnungen von Reitz abgeleiteten, molekularen Wellenfunktionen der Valenzelektronen berechnet und gute Vbereinstimmung mit der beobachteten Anisotropie fur Tellur erhalten. Es wird in der Analyse gefunden, daD etwa 2% Mischung von ,,bonding"-und ,,antibonding"-Zustinden im oberen Valenzbandzustand des Tellurs auftritt. Es sind weitere Berechnungen notwendig, nm die anisotrope chemische Verschiebung in Selen zii erklaren.

Solid-state selenium-77 NMR

“…Solid-state NMR investigations of elemental selenium have demonstrated the sensitivity of 77 Se chemical shifts to minor changes in the local environment since the initial investigation of a single crystal of trigonal selenium at 77 K (Table 2) [84]. This study indicated that the most shielded principal component lies nearly parallel to the direction of the helices [84][85][86]. Subsequent variable temperature experiments up to 480 K have demonstrated a general decrease in selenium shielding with increasing temperature for crystalline selenium, see Table 2 [87][88][89].…”

Observation of current-induced bulk magnetization in elemental tellurium

“…We estimated the angular difference to be approximately 6° by comparing the two-line spectrum with the shift parameters reported in ref. 31 . When the maximum current density of 82 A cm −2 with the pulse duration of 650 μs is applied to the sample, the temperature of the sample is estimated to have risen by 5 K at most; this estimate was obtained by calculating the product of the applied current and the voltage between the electrodes including the voltage drop due to the contact resistance.…”

Chirality-Induced Electrical Generation of Magnetism in Nonmagnetic Elemental Tellurium

“…3a, b and 5a). We estimated the angular differences between the magnetic field directions and the c axis to be approximately 7 • for Sample #1 and 9 • for Sample #2 by comparing the two-line spectrum with the shift parameters [34].…”

“…3 )tellurium [19]. The chirality of the covalent-bond helices determines the polarities of many physical properties, such as the angular-momentum texture in the k space [20][21][22], natural optical rotatory power [23][24][25][26], secondharmonic generation [27], piezoelectricity [28,29], shapes of etch pits [30], resonant diffraction with circularly polarized x rays [31,32], polarized neutron scattering [33], and NMR chemical shift [34] (see Supplemental Material [19]).…”