Mössbauer Effect in Iron under Very High Pressure

Pipkorn, D.N.; Edge, C. K.; Debrunner, Peter G.; Pasquali, G. De; Drickamer, H. G.; Frauenfelder, Hans

doi:10.1103/physrev.135.a1604

Cited by 158 publications

(40 citation statements)

References 28 publications

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“…Fe and Co undergo transitions into a nonmagnetic state at 14-25 [8,9] and 100-150 [10][11][12] GPa at room temperature, respectively. However, in these cases, the collapse of ferromagnetism is associated with structural transitions of the crystal structure.…”

mentioning

confidence: 99%

Hyperfine Splitting and Room-Temperature Ferromagnetism of Ni at Multimegabar Pressure

et al. 2013

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mentioning

confidence: 99%

Hyperfine Splitting and Room-Temperature Ferromagnetism of Ni at Multimegabar Pressure

et al. 2013

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“…The isomer shift systematics for cobalt-57 have intrigued many investi gators, and an explanation of these systematics was attempted fairly early by Walker, Wertheim, and Jaccarino (27). From pressure experi ments (9,17,20,22) AR/R for cobalt-57 is 1.8 Χ 10" 3 and negative (20,22). [The pressure experiments assume an isotropic compression.…”

Section: Nuclear Instruments and Methodsmentioning

confidence: 98%

“…[The pressure experiments assume an isotropic compression. Up to 240 kbars at room temperature, the pressure dependence of the isomer shift is given adequately (20,22) by the equation A(IS/Ap = (7.89 ± 0.31) Χ 10" 4 mm./sec. kbar.]…”

Section: Nuclear Instruments and Methodsmentioning

confidence: 99%

The Mössbauer Effect and Its Application in Chemistry

Herber

1967

Advances in Chemistry

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The Mössbauer effect involves the resonance fluorescence of nuclear gamma radiation and can be observed during recoilless emission and absorption of radiation in solids. It can be exploited as a spectroscopic method by observing chemically dependent hyperfine interactions. The recent determination of the nuclear radius term in the isomer shift equation for 119 Sn shows that the isomer shift becomes more positive with increasing s electron density at the nucleus. Detailed studies of the temperature dependence of the recoil-free fraction in 119 Sn and 129 I labeled SnI 4 show that the characteristic "Mössbauer temperatures," θ M , are dif ferent for the two atoms. These results are typical of the kind of chemical information which can be obtained from Mössbauer spectra. RudolphMössbauer in late 1957-1958 attempted to observe γ-ray -•^ resonance in such a way that the recoil energy which is lost in the usual nuclear gamma decay is compensated for by temperature broad ening-the so-called Doppler broadening observed in such γ-ray spectra. He chose iridium-191, with a γ-ray energy of 129 k.e.v. and a free-atom recoil energy of 0.05 e.v. The Doppler broadening at room temperature is such that the width of the gamma line is a factor of 2 larger than this. Therefore, the line emitted by the source and the line that can populate the ground state-first excited state transition in the absorber actually overlap-i.e., the total distance between E t -E R and E t + E B is about the same as the width of one of these lines. Figure 1 represents graphi cally the relationship among the line width, Γ, the transition energy, E t , and the recoil energy, E R .Môssbauer attempted to observe this resonance by studying his system at elevated temperatures, at which the overlap becomes reason-1 The Mössbauer Effect and Its Application in Chemistry Downloaded from pubs.acs.org by 79.110.25.164 on 06/23/16. For personal use only.

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“…8.5). Such experiments show that the iron transformation begins near 130 kbar and goes to completion for stresses greater than 150 kbar [25,26]. This behavior disagrees with equilibrium thermodynamics, which requires completed transformation to occur at constant stress when temperature is held constant for long times.…”

Section: Fast Reversible Phase Transition In Ironmentioning

confidence: 97%

“…[9,10] A number of static isothermal compression experiments on iron are shown in Fig. 8.5 that the transition from a body centered cubic (bcc or a) lattice to a hexagonal closed packed (hcp or e) lattice is initiated near 130 kbar and goes to completion for stresses greater than 145 kbar [25][26][27]. Giles, et al [26] found values of 133 kbar for the a !…”

Section: Fast Reversible Phase Transition In Ironmentioning

confidence: 99%

First-Order Polymorphic and Melting Phase Transitions Under Shock Loading

Forbes

2012

Shock Wave Compression of Condensed Matter

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Some materials at high pressure have structural arrangements of atoms and molecules that are at a lower energy state than that at (P ¼ 0, v o , T-293 K) conditions. When this occurs a thermodynamic force on the material exists to change the configuration to the new one. This process is called a first-order phase transition that is characterized by the coexistence of several thermodynamic phases. It is well established that condensed matter can also undergo thermodynamic second order phase transitions in electric and magnetic properties that are not treated in this book. Readers interested in second order phase transitions seen in dynamic experiments consult the literature especially the articles by Keeler and Royce [1].Static studies of phase transitions provide the baseline for understanding many phase transitions. They can show if the mixed phase region is in thermodynamic equilibrium or in a metastable state. Inferring phase transformations under dynamic loading from experimental static data is very useful. The first order guess of the phase seen in dynamic experiments will be the same as observed in static experiments but this needs to be verified in real-time dynamic experiments. One must keep in mind that under dynamic loading, phases other than that seen in static experiments are a possibility. This was seen in a recent study of shocked polycrystalline iron [2] where fcc phases occurred in certain oriented crystal grains. Note that this shock study using intense x-rays directly confirmed experimentally the majority of the iron transition was martensitic in nature, which agrees with static studies.The kinetics of the transformation determines whether a new configuration occurs under shock loading. If the transformation takes many microseconds to occur it will not be seen in standard shock wave experiments and the material will be put into a thermodynamic metastable state. Since dynamic loading is different than static compression some transitions that require cooperative lattice motion can be accelerated due to the shear in a shock wave. This is what happens in the body center cubic (bcc or a) to hexagonal closed packed (hcp or ɛ) lattice transition in iron [3] at 130 kbar. Keep in mind that due to creation of defects,

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Mössbauer Effect in Iron under Very High Pressure

Cited by 158 publications

References 28 publications

Hyperfine Splitting and Room-Temperature Ferromagnetism of Ni at Multimegabar Pressure

Hyperfine Splitting and Room-Temperature Ferromagnetism of Ni at Multimegabar Pressure

The Mössbauer Effect and Its Application in Chemistry

First-Order Polymorphic and Melting Phase Transitions Under Shock Loading

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