The acoustic paramagnetic resonance spectrum of chromous ions in magnesium oxide

Marshall, F G; Rampton, V. W.

doi:10.1088/0022-3719/1/3/306

Cited by 26 publications

(5 citation statements)

References 2 publications

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“…Acoustic paramagnetic resonance (APR), far-infrared (FIR), phonon-scattering, and thermal-conductivity experiments have been carried out on MgO:Cr 2+ , KMgF 3 :Cr 2+ , and CaO:Cr 2+ . – In these hosts, the chromous ion is embedded substitutionally for Mg 2+ or Ca 2+ at a site of approximately cubic symmetry and is very strongly coupled to the lattice vibrations. The energy splittings observed in these systems can be interpreted with the aid of Ham’s three-state model, assuming strong first-order and weak second-order Jahn–Teller coupling with very small lattice strain.…”

Section: Calculations and Discussionmentioning

confidence: 99%

Theory of High-Spin d⁴ Complexes: An Angular-Overlap Model Parametrization of the Ligand Field in Vibronic-Coupling Calculations

Carver

Thut

Noble

et al. 2008

J. Chem. Theory Comput.

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A new theoretical approach for the calculation of the electronic and molecular structures of octahedrally-coordinated high-spin d(4) complexes is described. A prescription for the construction of an effective (3)T1 + (5)E (O) Hamiltonian from the ligand-field matrices of a complex with general trigonal symmetry is given, where the ligand field is parametrized in terms of the angular-overlap model (AOM). The Jahn-Teller matrices for the (3)T1 + ((5)E⊗e) vibronic Hamiltonian are constructed and the lowest eigenvalues are calculated by a numerical method. The model obviates the need to assume a temperature dependence of bonding parameters, inherent to the conventional ligand-field-theory approach and is applicable over the whole range of vibronic-coupling strengths, as demonstrated by example calculations on the [Mn(OD2)6](3+) cation and MgO:Cr(2+).

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Section: Calculations and Discussionmentioning

confidence: 99%

Theory of High-Spin d⁴ Complexes: An Angular-Overlap Model Parametrization of the Ligand Field in Vibronic-Coupling Calculations

Carver

Thut

Noble

et al. 2008

J. Chem. Theory Comput.

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“…One (sample A) contained about 2000 ppm of chromium, and the other (B) was nominally pure but neutron activation analysis by the University Research Reactor service revealed 8 ppm chromium, 4 ppm nickel, 18 ppm manganese, and about 50 ppm iron. The reason for this choice of samples was twofold: (i) there is a wealth of information on the EPR of all magnetic ions in the cubic MgO lattice; (ii) we wanted to try to observe for the first time the EPR of the ion Cr2+, an ion known to be present in both 'pure' and chromiumdoped MgO but so far only detected by acoustic paramagnetic resonance (Marshall and Rampton 1968) and indirectly by its effect on thermal conductivity (Challis et a1 1968).…”

Section: Resultsmentioning

confidence: 99%

Thermal detection of the electron paramagnetic resonance of impurities in MgO

Moore

Al-Sharbati

1973

J. Phys. D: Appl. Phys.

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The magnetic resonance of iron-group impurities in dielectric host lattices with high Debye temperatures is shown to be easily detectable by the resulting rise in temperature on resonance of a sample weakly attached to a heat sink at 4 K. The heat causing the temperature rise is provided by spin-lattice relaxation in the sample, which is in a magnetic field and subject to electromagnetic radiation at the electron paramagnetic resonance (EPR) frequency. The experimental technique is very simple, and offers the possibility of studying those impurities with broad EPR lines and short spin-lattice relaxation times that are undetectable by conventional methods. In addition there is the possibility of investigating the subsequent thermal history of the monochromatic phonons released during spin-lattice relaxation. Experimental results for the thermal EPR spectrum of a variety of paramagnetic ions in MgO are presented, and the saturation behaviour of magnetic ions with widely varying strengths of coupling to the lattice is compared. Typically we find temperature rises of 10 mK from 1016 spins/cm3 with relaxation times 0·1 s, independent of the linewidth. These figures lead to an observed sensitivity of 1015 spins/cm3 with relaxation time 10−1 s or 1010 spins/cm3 with relaxation time 10−6 s, on the conservative assumption that 1 mK is the minimum detectable temperature rise.

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“…It is well established that thermal fluctuations lead to generation of an acoustic wave in a given medium 30 . In solids, there is a large body of knowledge on spin–phonon interaction 31 , 32 which leads to interesting physical effects like acoustic paramagnetic resonance in transition metals 33 , 34 . Acoustic waves influence the dynamics of charged particles and long range electron transfer under the impact of surface acoustic waves have been reported 35 .…”

Section: The Dynamics Of Nuclear Spin In a Magnetic Fieldmentioning

confidence: 99%

Generation of acoustic-Brownian noise in nuclear magnetic resonance under non-equilibrium thermal fluctuations

Sinha

2020

Sci Rep

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We present an analytical study on generation of acoustic-Brownian noise in nuclear magnetic resonance (NMR) induced as a result of thermal fluctuations of the magnetic moments under non-equilibrium thermal interactions which has not been explored independent of Nyquist–Johnson noise until now. The mechanism of physical coupling between non-equilibrium thermal fluctuations and magnetic moments is illustrated using Lighthill’s formulation on suspension dynamics. We discover that unlike Nyquist–Johnson noise which has a uniform spectral density across a range of frequencies, the spectral dependence of acoustic-Brownian noise decreases with an increase in frequency and resembles Brownian noise associated with a particle in a potential well. The results have applications in the field of image enhancement algorithm as well as noise reduction instrumentation in NMR systems.

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The acoustic paramagnetic resonance spectrum of chromous ions in magnesium oxide

Cited by 26 publications

References 2 publications

Theory of High-Spin d⁴ Complexes: An Angular-Overlap Model Parametrization of the Ligand Field in Vibronic-Coupling Calculations

Theory of High-Spin d⁴ Complexes: An Angular-Overlap Model Parametrization of the Ligand Field in Vibronic-Coupling Calculations

Thermal detection of the electron paramagnetic resonance of impurities in MgO

Generation of acoustic-Brownian noise in nuclear magnetic resonance under non-equilibrium thermal fluctuations

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The acoustic paramagnetic resonance spectrum of chromous ions in magnesium oxide

Cited by 26 publications

References 2 publications

Theory of High-Spin d4 Complexes: An Angular-Overlap Model Parametrization of the Ligand Field in Vibronic-Coupling Calculations

Theory of High-Spin d4 Complexes: An Angular-Overlap Model Parametrization of the Ligand Field in Vibronic-Coupling Calculations

Thermal detection of the electron paramagnetic resonance of impurities in MgO

Generation of acoustic-Brownian noise in nuclear magnetic resonance under non-equilibrium thermal fluctuations

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Theory of High-Spin d⁴ Complexes: An Angular-Overlap Model Parametrization of the Ligand Field in Vibronic-Coupling Calculations

Theory of High-Spin d⁴ Complexes: An Angular-Overlap Model Parametrization of the Ligand Field in Vibronic-Coupling Calculations