Spin-Phonon Magnetic Resonance of Conduction Electrons in Indium Antimonide Crystals
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Journal of Applied Spectroscopy, Vol. 87, No. 4, September, 2020 (Russian Original Vol. 87, No. 4, July–August, 2020)
SPIN-PHONON MAGNETIC RESONANCE OF CONDUCTION ELECTRONS IN INDIUM ANTIMONIDE CRYSTALS N. A. Poklonski,* A. N. Dzeraviaha, and S. A. Vyrko
UDC 621.315.592
Resonance absorption of radio waves (with a frequency of 10 MHz) by c-band electrons in indium antimonide crystals doped with hydrogen-like donors (tellurium atoms) at room temperature in an external magnetic field is theoretically studied. Known experimental data obtained for samples with electron concentrations in the range from 6·1015 to 5·1018 cm–3 are analyzed and interpreted. Resonant absorption of radio waves by n-InSb:Te crystals in a magnetic field is calculated to be due to spin-phonon resonance based on the law of conservation of energy and the quasi-wave vector for electrons and optical phonons. The resonance arises as a result of a spin-flip interaction of a c-band electron with an optical phonon, which is assisted by resonant absorption of radio waves in a magnetic field. A physical picture of the phenomenon is given. Analytical relations are presented. Calculations are carried out and are consistent with experimental data that could not previously be interpreted at all. Keywords: spin-phonon magnetic resonance, spin flip, electron, optical phonon, absorption of radio waves. Introduction. Crystalline layers of n-type InSb are used in spintronics devices [1] owing to the anomalous negative effective magnetic moment of the c-band electrons (|μB| ≈ 26 μB, where μB is the Bohr magnetron) [2]. The c-band electrons also have much greater drift mobility (under laboratory conditions) than those of Si, Ge, and diamond crystals. This enables fast-acting semiconducting instruments based on n-InSb to be fabricated. For example, a model for a high-frequency field transistor of InSb nanowires was proposed [3]. The above features are a consequence of undoped InSb crystals having a very small density of states c-band electron effective mass (m = 0.0136m0 [4, 5], where m0 is the electron mass in a vacuum). However, the effective mass m increases considerably upon increasing the concentration of free electrons (conductivity electrons) as a result of doping InSb with hydrogen-like donors [6]. Furthermore, InSb crystals are direct-bandgap narrowbandgap semiconductors [7]. The bandgap of Eg ≈ 0.18 eV at room temperature is much less than the electron affinity EA ≈ 4.6 eV [8]. The narrow bandgap between the bottom of the c-band and the top of the v-band complicates calculations of the one-electron band structure of InSb as compared to, e.g., analogous calculations for diamond and Si because strong spinorbit coupling of the c-band electrons with heavy and light v-band holes and holes in the spin-orbit decoupled v-band subband must be taken into account [7, 9]. Hall sensors, which are widely used to measure magnetic field strength, were prepared from InSb crystals [10]. All this is responsible for the practical importance of studying the effects of element
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