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1.
The temperature dependence of the 55Mn and 19F NMR in antiferromagnetic FeF2 with 1% Mn impurities was used to determine the magnetizations σi, σnn and σnnn vs. T for the impurity and neighboring Fe ions. σi vs. T was found to be well described by an effective field theory in agreement with the thermodynamic Greens' function prediction for an impurity mode below the host-magnon band. The magnitude of the FeMn nnn exchange interaction J′2 in Fe:MnF2 and Mn:FeF2 differ slightly from each other but the nn interaction J′1 changes sign. 相似文献
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S.M. Rezende Cid.B. de Araujo E. Montarroyos V. Jaccarino 《Solid State Communications》1980,35(8):627-630
A study of the local magnon mode in FeF2 crystals with Mn2+ impurities by inelastic Raman light scattering is presented. Though the interaction between the radiation and the Mn spins is negligible the scattering by the s0 local mode is very strong. The data of the frequency and the scattering intensity are analyzed in terms of a magnetization coupled mode approach. 相似文献
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K. Haneda X. Z. Zhou A. H. Morrish R. J. Pollard T. Majima 《Hyperfine Interactions》1990,54(1-4):551-556
Ultrafine antiferromagnetic FeF2 particles (<10 nm) were prepared by a new technique, viz, the SF6-sensitized infrared photodecomposition of Fe(CO)5 induced by a transversely excited atmospheric (TEA) CO2 laser. The magnetic properties have been examined by57Fe Mössbauer spectroscopy. At low temperatures the magnetic hyperfine field decreases faster with increasing temperature than the hyperfine field of the bulk; this behavior appears to be consistent with collective magnetic excitations. The transition between the paramagnetic and antiferromagnetic states takes place at a higher temperature and over a broader range as compared to the bulk. FeF2 ultrafine particles are relatively sensitive to oxidation; cubic-type iron oxide is formed. 相似文献
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A. Stasch 《Zeitschrift für Physik B Condensed Matter》1980,37(4):289-297
It is shown theoretically that, in the presence of a strong magnetic field, effects due to the interaction betweenB
1g
,E
g,TA
phonons and magnons should be important in the Raman and infrared absorption spectrum of FeF2. As a result the two magnon line should split. A microscopic Hamiltonian for the interactions has been derived. The calculated values of theE
g phonon-one magnon interaction, 9.9 cm–1, and of theB
1g
phonon-two magnon coupling, 6.3 cm–1, are comparable to those in FeCl22H2O metamagnet, in which C phonon-magnon hybrydization has been observed [1]. It is shown that hybridization between two magnon andB
1g
orTA
phonon can occur in FeF2 if the magnon energy approaches the phonon energy due to increasing magnetic field or increasing temperature.On the leave from Technical University, Pozna, Institute of Physics, Pozna 61–138 Piotrowo 3, Poland 相似文献
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The characteristics of the spin-flop transition in K2FeF5 and Rb2FeF5 are found by Mössbauer spectroscopy to be very different, and are discussed in relation to the ordered magnetic structures of the two systems. 相似文献
7.
With electron spin resonance (ESR) spectroscopy, we revealed various free radicals in commercially available pepper in Japan
before and after γ-irradiation. The representative ESR spectrum of the pepper is composed of a sextet centered atg=2.0, a singlet at the sameg-value and a singlet atg=4.0. The first signal is attributable to a signal with hyperfine interactions of the Mn2+ ion (hyperfine constant, 7.4 mT). The second signal is due to an organic free radical apparently induced by a sterilization
process. The third signal may originate from the Fe3+ ion in the nonheme proteins. The progressive saturation behavior at various microwave power levels indicated quite different
relaxation behaviors of those radicals. Namely, the peak intensity of the organic free radical component decreases in a monotonic
fashion, whereas the Mn2+ and Fe3+ ESR signals substantially remain constant. This evidences the presence of three independent radicals in the pepper before
irradiation. Upon γ-irradiation, a new pair of signals appeared in the pepper. The progressive saturation behavior of the
pair peaks after the irradiation showed a quite different behavior as compared with the free radical centered atg=2.0. For the measure of irradiation effects, we propose a universal index for the ESR analysis of irradiated dry foods. 相似文献
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W. Becker M. O. Scully M. S. Zubairy Y. Ben-Aryeh A. Rosenberg J. Felsteiner J. Politeh M. P. De Pascale G. Giordano G. Matone P. Picozza R. Caloi L. Casano M. Mattioli E. Poldi D. Prosperi C. Schaerf G. Dahlbacka R. Dukart R. Fortner D. Dietrich R. Stewart F. De Martini M. Foresti J. Slater D. Quimby L. Nelson R. Center T. Churchill J. Adamski R. H. Pantell T. I. Smith 《Applied physics. B, Lasers and optics》1982,28(2-3):150-154
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The VF3-type compounds MF3 with M = Fe and Ga have been studied by high-pressure energy-dispersive X-ray diffraction. The compression mechanism was found to be highly anisotropic for both compounds, with the c-axis showing little pressure dependence. The volume reduction is mainly achieved through coupled rotations of the MF6 octahedra around the c-axis, which reduces the length of the a-axis. The compression mechanism of both compounds is reasonably well described in terms of deformation of an 8/3/c2 sphere-packing model up to the pressures where the fluorine atoms become hexagonally close-packed. It is proposed that both compounds enter a phase with the fluorine atom arranged in a “super-dense” sphere packing at higher pressures. The zero pressure bulk modulus of FeF3 and GaF3 was determined as 12(2) and 37(3) GPa, respectively, and a scaling relation between the zero pressure bulk modulus and unit cell volumes was found for TiF3, CrF3, FeF3 and GaF3. 相似文献
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《Journal of magnetism and magnetic materials》1995,146(3):L241-L246
55Mn nuclear magnetic resonance has been measured for both cubic C15 and hexagonal C14 HoMn2. In the ordered state, we found a high-frequency signal, which can be assigned to magnetic Mn atoms, for both C15 and C14 phases together with a low-frequency signal from non-magnetic Mn atoms. The results of the spin-spin relaxation time T2 in the ordered state and the NMR spectra in the paramagnetic state are also given to discuss the magnetic instability and the magnetic structure. 相似文献
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Free electron laser study of the suppression of non-radiative scattering processes in semiconductors
《Infrared Physics & Technology》1999,40(3):231-238
A brief review is given of pump–probe studies of far infrared inter-sub-level relaxation between conduction band states in doped `quasi' quantum dots (created by the application of a magnetic field along the growth direction of an InAs/AlSb quantum well) and of mid-infrared (MIR) interband recombination in narrow gap semiconductors, using the free electron laser at FOM-Rijnhuizen (FELIX). In the former case, the longitudinal optic (LO) phonon scattering rate is shown to be suppressed by a factor of about 100 when the Landau level separation is off-resonance with the optical phonon energy; in the latter case, Auger recombination is shown to be substantially suppressed in the lead salts due to their `mirror' energy band structure. 相似文献
16.
The magnetic spin structure factor of FeF2 has been directly determined from high energy magnetic x-ray diffraction at 115 keV photon energy. A pure spin moment of mu = 4.01(5)mu(B) was observed, which agrees very well with the spin moment of the free Fe2+ ion and differs significantly from values of the total magnetic moment obtained by other methods. The magnetic phase transition of FeF2 has been carefully investigated and values for the critical exponent of the order parameter obtained by other techniques have been confirmed. 相似文献
17.
By using the surface and element specificity of soft x-ray magnetic dichroism we provide direct experimental evidence for two different types of interfacial uncompensated Fe moments in exchange biased Co/FeF2 bilayers. Some moments are pinned and coupled antiparallel to the ferromagnet (FM). They give rise to a positive exchange bias and vanish above T(N) = 78 together with the antiferromagnet (AF) order. Other interfacial Fe moments are unpinned and coupled parallel to the FM. They persist up to 300 K and give rise to magnetic order at the AF surface even above T(N) . 相似文献
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A Mössbauer measurement of the pressure dependence of the Néel temperature in FeF2 is reported. Up to the maximum pressure of 50 kbar TN increases at the rate of 0.27 ± 0.03°K/kbar. When this pressure dependence is converted to volume dependence, the result, d In TN/d In V = 3.2 ± 0.3, is found to obey the rule” established by Bloch for a wide variety of antiferromagnetic insulators. 相似文献
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A new mechanism of light amplification on free-free electron transitions is considered, and light amplification is shown to be considerable. The amplification coefficient is calculated. 相似文献