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This updated and significantly expanded second edition of \"The Mössbauer Effect\" describes the basic physics of the Mössbauer effect and its applications in a variety of fields including physics, chemistry, materials science, biology, mineralogy and archaeology.

La2SrFe2TiO9 Triple perovskite, prepared via the solid-state reaction method, exhibits an orthorhombic structure with space group Pnma as confirmed by X-ray diffraction studies. The dielectric properties of the material were investigated in the temperature range of 100–400 K within the frequency range of 20 Hz–2 MHz. We have seen that the material’s dielectric constant decreases with the increase in the frequency due to the space polarisation mechanism and its increase with temperature due to the thermal activation of the charge carriers. Jonscher’s Power law explains the AC conductivity mechanism of the sample, and we have seen that the material shows two types of conduction mechanisms: the Carrier Barrier Hopping Mechanism (CBH) and the Non-overlapping Small polar tunneling (NSPT) model. The shifting of the relaxation peak towards a higher frequency with an increase in temperature ensures its thermally activated nature. From the ferroelectric studies, we have seen that the material possesses ferroelectric behavior. The valence state of the Fe atom, as determined from measurements of the Mossbauer effect of 57Fe at room temperature, indicated that the iron ion exists in the Fe3+ high spin state based on the values obtained for the isomer shift. Additionally, the material's ability to exhibit high conductivity coupled with low tangent loss, attributed to oxygen vacancies, establishes La2SrFe2TiO9 as a highly promising option for use in electronics, magnetoelectric, spintronics, and photocatalysis.

Transition metal takes charge The introduction of 'foreign' elements into transition-metal oxides (called chemical doping) can change the valence state of the metal's cations and hence modify the physical properties of the material as a whole. These changes can be dramatic, for example causing high-temperature superconductivity in copper oxides and colossal magnetoresistance in manganese oxides. Youwen Long et al . have identified an oxide system, the perovskite LaCu 3 Fe 4 O 12 , in which changes in valence state occur when charge is shuffled between different cations (iron and copper) in the host structure, rather than via doping. As a result, the material can be reversibly transformed from one possessing iron in an unusually high Fe 3.75+ state (partnered with fairly common Cu 2+ ions) to one possessing rare Cu 3+ ions. These changes are reflected in the magnetic and electronic properties of the material and, intriguingly, the material contracts slightly on being warmed through the transition. The temperature sensitivity of this effect makes it a strong candidate for technological applications. This paper identifies an oxide system where changes in valence state occur as a result of charge being shuffled between different cations in the host structure, rather than via doping, this charge transfer being sensitive to temperature. As a result, the material can be reversibly transformed from one possessing iron in an unusually high Fe3.75+ state to one possessing rare Cu3+ ions. These changes are reflected in the magnetic and electronic properties of the material and, intriguingly, are accompanied by negative thermal expansion. Changes of valence states in transition-metal oxides often cause significant changes in their structural and physical properties 1 , 2 . Chemical doping is the conventional way of modulating these valence states. In ABO 3 perovskite and/or perovskite-like oxides, chemical doping at the A site can introduce holes or electrons at the B site, giving rise to exotic physical properties like high-transition-temperature superconductivity and colossal magnetoresistance 3 , 4 . When valence-variable transition metals at two different atomic sites are involved simultaneously, we expect to be able to induce charge transfer—and, hence, valence changes—by using a small external stimulus rather than by introducing a doping element. Materials showing this type of charge transfer are very rare, however, and such externally induced valence changes have been observed only under extreme conditions like high pressure 5 , 6 . Here we report unusual temperature-induced valence changes at the A and B sites in the A-site-ordered double perovskite LaCu 3 Fe 4 O 12 ; the underlying intersite charge transfer is accompanied by considerable changes in the material’s structural, magnetic and transport properties. When cooled, the compound shows a first-order, reversible transition at 393 K from LaCu 2+ 3 Fe 3.75+ 4 O 12 with Fe 3.75+ ions at the B site to LaCu 3+ 3 Fe 3+ 4 O 12 with rare Cu 3+ ions at the A site. Intersite charge transfer between the A-site Cu and B-site Fe ions leads to paramagnetism-to-antiferromagnetism and metal-to-insulator isostructural phase transitions. What is more interesting in relation to technological applications is that this above-room-temperature transition is associated with a large negative thermal expansion.

The Error and Monitor signals of the Mössbauer driver can be used to infer the true velocity in the acquisition of a Mössbauer spectrum. This information can be recorded to substantially improve the collected data. It can be used to perform quality control of the spectra, validate regions of good linearity and correct non-linearities. In particular the error waveform is essential to account for possible deviations of the channel-to-velocity relation from the expected one. These deviations are mainly due to the physical limitations of the feedback control system. They are almost impossible to anticipate and they vary considerably when modifying the amplitude or shape of the velocity reference, or when modifying the parameters of the closed-loop control system. The sampling of the Error and Monitor waveforms can be carried out with a standard digital oscilloscope, while maintaining a correct synchronization and resolution, necessary for a correct post-analysis. In this paper a method for wave acquisition and reconstruction is proposed. The effects of non-controlled oscillations at the abrupt changes of velocity variation in alpha Fe spectra are discussed. It is also shown how the acquisition can be performed remotely and automatically, without disturbing the measurement or decreasing the efficiency of the spectrometer.

A series of high iron content boro-phosphate glasses having composition of 30P 2 O 5 -70B 2 O 3 -xFe 2 O 3 );0 ≤ x ≤ 80 wt% was prepared by conventional melt quench method. Mössbauer effect (ME), infrared (IR) and electron spin resonance (ESR) were used to study the behavior of iron brought into borophosphate glass and its effect on the structure of the glass. The results of the glasses containing from 10 to 80 wt% Fe 2 O 3 indicated that iron is present in the glass in the form of Fe 3+ and Fe 2+ , i.e. in tetrahedral and various octahedral symmetric sites. Electron paramagnetic resonance (EPR) spectra were utilized to investigate the glass structure. The analysis shows a well-defined signal at g = 2.04 characteristics for Fe 3+ ions and the intensity increases with increasing Fe 2 O 3 concentration before gamma irradiation. After exposing the samples to different doses of gamma irradiation up to 30 kGy; the EPR signal intensity decreases for the samples with a low Fe 2 O 3 concentration (i.e. 10% and 40%), which can be used as radiation indicators. For glass with high iron concentrations above 40%, the intensity of the EPR signal remains approximately constant and therefore, high iron concentrations of this glass can be used for radiation protection purposes.

The Mössbauer effect (ME) spectroscopy is a powerful tool to obtain information about magnetic nanoparticles (NP). Here we correlate parameters that can be obtained from a ME spectrum (relative fractions of magnetite and maghemite and the volume dependent parameter λ=KV/kBT ) with other relevant quantities, such as DC saturation magnetization and X-ray diffraction NP mean diameter, D XRD . The study was performed on the decanted pellets of six different batches of NP obtained using the same synthesis procedure. It was observed that λ1/3 presents a linear correlation with D XRD from which the effective anisotropy K for the entire ensemble of the batches could be calculated. The fraction of magnetite retrieved from ME spectra was well correlated to the saturation magnetization. In addition, it was observed that the magnetic response of the supernatant obtained after washing and centrifuging the synthesis product, decreases with λ , according to the fact that larger NP decant more easily during centrifugation.

Surface magnetism of Fe (001) was investigated by the in situ iron-57 probe layer method with a synchrotron Mössbauer source. The observed layer-by-layer internal hyperfine field shows a marked reduction at the surface and an oscillatory behavior with increasing depth in the individual layers below the surface. The calculated layer-by-layer hyperfine interactions (hyperfine field, isomer shift, and quadrupole shift) were consistent with the experimental results. The results give direct evidence for the magnetic Friedel oscillations, penetrating several layers from the Fe (001) surface.

The web-accessible online database (WAD) of the Mössbauer Effect Data Center (MEDC) is one of the worldwide available information services provided by MEDC to the scientific community. It is based on the uniquely wide scope Mössbauer spectroscopy database that has been compiled and maintained by MEDC since the 1960’s. Following enhancements applied to the capabilities of the MEDC core database in connection with the development of a new database management software named “MEDC DBM”, the development of a new web-accessible online database (MEDC WAD) was started in 2019. Here we introduce the current state and the main features of the newly developed MEDC WAD system with emphasis put on its novel and rather unique attributes that can effectively aid the scientific research process in the field of Mössbauer spectroscopy.

The measurements of magnetic hyperfine fields (MHF), H hf , and isomer shift, δ, in Y(Fe 1 – x Ni x ) 2 intermetallic compounds (the MgCu 2 structure type) synthesized at high pressure are performed. The MHF values that appear on 57 Fe nuclei at a nickel concentration x below 20 at % practically do not change and are approximately equal to 22 T, and in the range from x = 0.4 to 0.98 they decrease linearly with an increase in the Ni concentration. However, linear extrapolation of the hyperfine field as a function of Ni concentration does not lead to its disappearance in YNi 2 . For YFe 2 , the rotation of the easy axis from the [101] direction to the [111] direction with increasing temperature is found. As the Ni concentration increases to x = 0.3 at a temperature of 5 K, the easy magnetization axis [101] is observed, and at x = 0.4 the axis changes direction to [100]. Based on the shape of the concentration dependence of the hyperfine field, it is assumed that during the crystallization of Y(Fe 1 – x Ni x ) 2 under high pressure conditions, a magnetic moment exists on Ni ions. First-principles calculations of magnetic properties and hyperfine interactions are performed, which are consistent with experiment.

The changes of short range ordering and electron density were investigated by means of the nuclear gamma-resonance and the positron annihilation spectroscopies in model alloys containing tungsten, chromium, molybdenum, and vanadium used as dopants. The change of the short-range ordering parameter sign was detected in alloys containing vanadium. Different ordering was also observed in binary and ternary iron alloys. It was shown that dislocations were the main defects in these materials after rolling. nema