Probing the Yb3+^{3+} spin relaxation in Y0.98_{0.98}Yb0.02_{0.02}Ba2_{2}Cu3_{3}Ox_{x} by Electron Paramagnetic Resonance

The relaxation of Yb$^{3+}$ in YBa$_{2}$Cu$_{3}$O$_{x}$ ($6<x<7$) was studied using Electron Paramagnetic Resonance (EPR). It was found that both electronic and phononic processes contribute to the Yb$^{3+}$ relaxation. The phononic part of the relaxation has an exponential temperature dependence, which can be explained by a Raman process via the coupling to high-energy ($\sim$500 K) optical phonons or an Orbach-like process via the excited vibronic levels of the Cu$^{2+}$ ions (localized Slonczewski-modes). In a sample with a maximum oxygen doping $x$=6.98, the electronic part of the relaxation follows a Korringa law in the normal state and strongly decreases below $T_{c}$. Comparison of the samples with and without Zn doping proved that the superconducting gap opening is responsible for the sharp decrease of Yb$^{3+}$ relaxation in YBa$_{2}$Cu$_{3}$O$_{6.98}$. It was shown that the electronic part of the Yb$^{3+}$ relaxation in the superconducting state follows the same temperature dependence as $^{63}$Cu and $^{17}$O nuclear relaxations despite the huge difference between the corresponding electronic and nuclear relaxation rates.Comment: 8 pages, 6 figure

Spin Texture and Spin Dynamics in Superconducting Cuprates Near the Phase Transition Revealed by the Electron Paramagnetic Resonance

© 2016, Springer Science+Business Media New York.A short review of experimental results and theoretical models of the spin texture and spin dynamics in superconducting cuprates near the phase transition developed on the basis of the EPR measurements is given. Distortions of the long-range antiferromagnetic order in the YBa2Cu3O6+y were investigated for y= 0.1 - 0.4 using Yb3 + ions as the EPR probe. In weakly doped samples with y= 0.1 , a strong anisotropy of the EPR linewidth is revealed which was related to the indirect spin–spin interaction between the ytterbium ions via antiferromagnetic spin-waves. In the case of the doping level y= 0.2 - 0.3 , the EPR signal consists of narrow and broad lines, which were attributed to formation of charged domain walls. A theoretical analysis is well consistent with experimental results for the case of coplanar elliptical domain walls. A discussion of possible reasons for the observed unusual planar oxygen isotope effect on a critical temperature Tc related to charge heterogeneity in underdoped cuprates is given

Spin-phonon interaction and the EPR linewidth in La2CuO4 and related cuprates

The spin-phonon interaction is derived for Cu2+ ions strongly coupled by the Isotropic exchange interaction. It is shown that in a two-dimensional quantum Heisenberg antiferromagnetic this interaction due to its antisymmetric structure couples the phonon modes near the wave vectors (±π/a, ±π/a) to the staggered magnetization. A contribution of the spin-phonon interaction to the EPR linewidth is calculated and its temperature dependence compared with other sources of the broadening. © 1999 Plenum Publishing Corporation

Magnetic properties and spin kinetics of a heavy-fermion Kondo lattice

A review of peculiarities of magnetic properties and spin kinetics of a heavy-fermion Kondo lattice revealed by electron spin resonance (ESR) experiments and their theoretical analysis is given. Among the issues discussed in some detail are the renormalization of spin kinetics coefficients due to the Kondo effect, formation of the collective spin modes of the Kondo ions and wide-band conduction electrons, unexpected behavior of ESR parameters as functions of temperature and magnetic fields. Special attention is focused on the possible role of the Kondo effect for the ESR signal existence at low temperatures

Electron paramagnetic resonance in superconducting cuprates

© 2017, Springer International Publishing AG.The way to a discovery of the high temperature superconductivity (HTSC) was started by Alex Müller with his study of partially covalent character of transition elements in oxides having perovskites structure by the electron paramagnetic resonance (EPR) method. It was actually the beginning of his scientific carrier: the first results were obtained in his thesis “Paramagnetische Resonanz von Fe3+ in SrTiO3 Einkristall” [1]. It is appropriate to remind that the discovered many years later superconducting cuprates have just the perovskites structure. Between the first step and this discovery were obtained a long chain of important results concerning the Jahn–Teller effect, structural phase transitions, photochromism, ferroelectricity, itinerant polarons and other properties of perovskites using the EPR and other methods. The relevant original works (concluded by the HTSC discovery) are collected in a volume “Properties of Perovskites and Other Oxides”, containing 562 pages [2]. It seems that these milestones on the way to a discovery were not occasional ones. From one hand a deep insight into condensed matter physics from the very beginning became possible due to a very good background: in his student time Alex Müller had a course of lectures in theoretical physics given by Wolfgang Pauli during four semesters. On the other hand there were some stimuli, which supported the following investigations of the perovskites properties. One of them was quite unusual: a lofty dream which had Alex about that time. A description of this dream can be found in the KAM’s article “Annäherungen ans Feuer” (“Approaching to a fire”), which was published in a volume dedicated to a psychiatrist C.G. Jung and a writer E. Jünger [3]. Below is given my attempt to translate it from German (page 39): “In a dream I saw Wolfgang Pauli sitting similar to Buddha in a deep meditation (1.5 years before his death), having in his right hand a high-symmetric crystal of SrTiO3 with a cubic symmetry of the lattice. A coming white beam of light was decomposed by it into the colored spectra. This dream, looking back now, was for me during four decades decisive, namely for my scientific research and its success, and for my health too.

Spin Texture and Spin Dynamics in Superconducting Cuprates Near the Phase Transition Revealed by the Electron Paramagnetic Resonance

© 2016 Springer Science+Business Media New YorkA short review of experimental results and theoretical models of the spin texture and spin dynamics in superconducting cuprates near the phase transition developed on the basis of the EPR measurements is given. Distortions of the long-range antiferromagnetic order in the YBa(Formula presented.)Cu(Formula presented.)O(Formula presented.) were investigated for (Formula presented.) using Yb(Formula presented.) ions as the EPR probe. In weakly doped samples with (Formula presented.), a strong anisotropy of the EPR linewidth is revealed which was related to the indirect spin–spin interaction between the ytterbium ions via antiferromagnetic spin-waves. In the case of the doping level (Formula presented.), the EPR signal consists of narrow and broad lines, which were attributed to formation of charged domain walls. A theoretical analysis is well consistent with experimental results for the case of coplanar elliptical domain walls. A discussion of possible reasons for the observed unusual planar oxygen isotope effect on a critical temperature T(Formula presented.) related to charge heterogeneity in underdoped cuprates is given

Magnetic properties and spin kinetics of a heavy-fermion Kondo lattice

© B.I. Kochelaev, 2017.A review of peculiarities of magnetic properties and spin kinetics of a heavy-fermion Kondo lattice revealed by electron spin resonance (ESR) experiments and their theoretical analysis is given. Among the issues discussed in some detail are the renormalization of spin kinetics coefficients due to the Kondo effect, formation of the collective spin modes of the Kondo ions and wide-band conduction electrons, unexpected behavior of ESR parameters as functions of temperature and magnetic fields. Special attention is focused on the possible role of the Kondo effect for the ESR signal existence at low temperatures

Semen A Altshuler: Smentor, teacher

International Conference "Resonances in Condensed Matter" is devoted to 100 years of the birthday of the Corresponding member of Academy of Sciences of the USSR, Professor of the Kazan University Semen Alexandrovich Altshuler (1911-1983). He is well known by pioneer works on EPR, the prediction and grounds for an existence of the neutron magnetic moment, the prediction and the theory of the acoustic paramagnetic resonance, and as a founder of the Kazan scientific school "Magnetic radiospectroscopy of condensed matter" (with E K Zavoiskii and B M Kozyrev)

OBSERVABILITY OF PARAMAGNETIC ACOUSTIC RESONANCE IN LIQUID CRYSTALS.

The observability of paramagnetic acoustic resonance in liquid crystals was studied. The resonance change in the penetration depth of an ultrasonic shear wave in a nematic liquid crystal, and the ultrasound resonance absorption coefficient in a smectic A liquid crystal, were calculated in the hydrodynamic approximation. The conditions for observability of the effect were determined