Ssbauer Spectra Research Articles

Negative ionic states of tin in the oxide superconductor Sr3−xSnO revealed by Mössbauer spectroscopy

We report the temperature variation of the $^{119}$Sn-M\"{o}ssbauer spectra of the antiperovskite (inverse perovskite) oxide superconductor Sr$_{3-x}$SnO. Both superconductive (Sr-deficient) and non-superconductive (nearly stoichiometric) samples exhibit major $\gamma$-ray absorption with isomer shift similar to that of Mg$_2$Sn. This fact shows that Sr$_{3-x}$SnO contains the metallic anion Sn$^{4-}$, which is rare especially among oxides. In both samples, we observed another $\gamma$-ray absorption with a larger isomer shift, indicating that there is another ionic state of Sn with a higher oxidation number. The temperature dependence of the absorption intensities reveals that the Sn ions exhibiting larger isomer shifts have a lower energy of the local vibration. The larger isomer shift and lower vibration energy are consistent with the values estimated from the first-principles calculations for hypothetical structures with various Sr-deficiency arrangements. Therefore, we conclude that the additional $\gamma$-ray absorptions originate from the Sn atoms neighboring the Sr deficiency.

Analysis of Cd2+ and In3+ ions doping on microstructure, optical, magnetic and mo¨ssbauer spectral properties of sol-gel synthesized BaM hexagonal ferrite based nanomaterials

Abstract Precise studies of cadmium and indium doped barium hexagonal ferrites having chemical composition Ba0.7Nd0.3Cdx/2Inx/2Fe12-xO19 (x = 0.0, 0.1, 0.2, 0.3) have been performed by sol-gel auto-combustion method in which ethylene glycol was used as a gel precursor. The structural, morphological, optical, elemental and magnetic properties have been studied by using various techniques like XRD, FESEM, FTIR, EDS and VSM. The XRD patterns shows characteristic (110), (008), (107), (114), (108), (203), (205), (206), (1011), (300), (217), (2011), (220), (2014) peaks along with the presence of secondary phase confirming the formation of hexagonal structure with an average crystallite size of 43–59 nm. FESEM supports the formation of hexagonal, dense and agglomerated nanoparticles. The Vibronic study using infrared radiation was carried by FTIR analysis reveal the various configuration modes with hexagonal symmetry of prepared nanoparticles. The magnetic measurements have been studied at room temperature indicates that saturation magnetization (Ms) and magnetic moment (nB) found to be of range 40–86 emu/g and 7.97–17.23 μB. The precise magnetic studies made it possible to reveal that saturation magnetization (Ms) increases with the cadmium and indium concentration for x = 0.1 and after that it decreases for x = 0.2, 0.3 which may be due to the difference in the magnetic moments of Cd, In and Fe ions. Due to high value of saturation magnetization (Ms), it can be used for applications in the field of high density recording storage devices and also, this magnetic change has been explained on the basis of exchange interactions. The room temperature M o ¨ ssbauer spectra of all the nano-sized materials shows normal Zeeman splitting consisting of six merged line patterns which indicates the formation of ferromagnetic phase that supports the magnetic properties.

First-principles study of intermediate-spin ferrous iron in the Earth's lower mantle

Spin crossover of iron is of central importance in solid Earth geophysics. It impacts all physical properties of minerals that altogether constitute $\sim 95$ vol\% of the Earth's lower mantle: ferropericlase [(Mg,Fe)O] and Fe-bearing magnesium silicate (MgSiO$_3$) perovskite. Despite great strides made in the past decade, the existence of intermediate-spin (IS) state in ferrous iron (Fe$^{2+}$) (with total electron spin $S=1$) and its possible role in the pressure-induced spin crossover in these lower-mantle minerals still remain controversial. Using density functional theory $+$ self-consistent Hubbard $U$ (DFT$+U_{sc}$) calculations, we investigate all possible types of IS states of Fe$^{2+}$ in (Mg,Fe)O and (Mg,Fe)SiO$_3$ perovskite. Among the possible IS states in these minerals, the most probable IS state has an electronic configuration that significantly reduces the electron overlap and the iron nuclear quadrupole splitting (QS). These most probable IS states, however, are still energetically disfavored, and their QSs are inconsistent with M\"{o}ssbauer spectra. We therefore conclude that IS Fe$^{2+}$ is highly unlikely in the Earth's lower mantle.

Low-temperature magnetic properties ofNpNi5

We present the result of an extended experimental characterization of the hexagonal intermetallic Haucke compound NpNi$_{5}$. By combining macroscopic and shell-specific techniques, we determine the 5$f$-shell occupation number $n_f$ close to 4 for the Np ions, together with orbital and spin components of the ordered moment in the ferromagnetic phase below T$_C$ = 16 K ($\mu_{S}$ = -1.88~$\mu_{B}$ and $\mu_{L}$ = 3.91~$\mu_{B}$). The apparent coexistence of ordered and disordered phases observed in the M\"{o}ssbauer spectra is explained in terms of slow relaxation between the components of a quasi-triplet ground state. The ratio between the expectation value of the magnetic dipole operator and the spin magnetic moment ($3\langle T_{z}\rangle/ \langle S_{z}\rangle$ = +1.43) is positive and large, suggesting a localized character of the 5$f$ electrons. The angular part of the spin-orbit coupling ($\langle\vec{\ell}\cdot\vec{s}\rangle$ = -5.55) is close to the value of -6.25 calculated for trivalent Np ions in intermediate coupling approximation. The results are discussed against the prediction of first-principle electronic structure calculations based on the spin-polarized local spin density approximation plus Hubbard interaction, and of a mean field model taking into account crystal field and exchange interactions.

M형 Ba-Ferrite에서 Fe 이온의 열 진동에 관한 연구

M형 Ba-ferrite 결정에서 5가지 자리에 위치한 Fe 이온의 열 진동에 관하여 M<TEX>$\ddot{o}$</TEX>ssbauer 분광법과 Raman 분석으로 연구하였다. 결정의 c-축 방향을 기준으로 감마선을 여러 방향으로 조사하여 각 방향에 대한 열진동의 형태를 측정 분석하였다. 특히 2b 자리에서 c-축 방향의 진동은 다른 방향 보다 매우 활발하여 M<TEX>$\ddot{o}$</TEX>ssbauer 공명 흡수에 큰 변화를 일으키고 있으며 Raman 측정에서도 2b 자리의 진동이 매우 크게 나타나는 특이한 성질을 나타내고 있다. M<TEX>$\ddot{o}$</TEX>ssbauer and Raman spectrum studies have been carried out on the 2b-site Fe ion in the Ba-ferrite (M-type). The thermal dynamics of Fe ion was analyzed by M<TEX>$\ddot{o}$</TEX>ssbauer spectra at different angles between the <TEX>$\gamma$</TEX>-ray direction and c-axis. The vibration on the 2b-site was more active compare to other direction and had very strong intensity in the Raman spectrum.

제주도 북동부 지역 스코리아 내의 철 화합물에 대한 자기적 성질

제주도 북동부 송당리 일원에 형성된 오름에서 채취한 스코리아의 화학적 조성 및 산화철의 원자가상태와 자기적 성질을 조사하였다. X-선 회절법을 이용하여 분석한 결과 이 지역의 스코리아들은 <TEX>$SiO_2$</TEX>와 장석이 주를 이루고 소량의 철 산화물이 확인되었다. M<TEX>$\ddot{o}$</TEX>ssbauer 분광법을 통해 광물 내의 철 성분들이 어떤 형태를 이루는지 살펴본 결과 olivine인 규산염과 pyroxene, ilmenite 형태의 상자성 철산화물 및 상온에서 반강자성 및 강자성 물질인 산화철 및 silicate mineral 등이 존재하였다. 철 화합물의 원자 가상태는 대부분 olivine과 pyroxene에서 <TEX>$Fe^{3+}$</TEX>이 존재하고 olivine, pyroxene과 ilmenite에 의해 소량의 <TEX>$Fe^{2+}$</TEX> 성분이 존재하고 있음을 알 수 있었고. 그 외에도 산화철 및 silicate mineral로 추정되는 흡수선도 관측되었다. 따라서 이 지역 대부분의 스코리아내의 철에 대한 주 원자가 상태는 <TEX>$Fe^{3+}$</TEX>과 <TEX>$Fe^{2+}$</TEX>가 공존하는 것으로 분석되었다. Fe compounds of scoria samples distributed in Songdang-ri positioning north-eastern area of Jeju island were investigated by means of X-ray diffractometry (XRD) and <TEX>$^{57}Fe$</TEX> M<TEX>$\ddot{o}$</TEX>ssbauer spectroscopy. The samples were prepared from six parasite. We found that the samples were composed of a typical olivine, pyroxene, ilmenite, <TEX>$SiO_2$</TEX>, anorite and anorthoclase, M<TEX>$\ddot{o}$</TEX>ssbauer spectrum of the most scoria samples are shown doublets and sextets of olivine, doublets of pyroxene, ilmenite and silicate minerals. And the valence states of Fe ion of the scoria samples in this area are chiefly 3+ charge state and a little 2+ charge state.

Self-doping effect and successive magnetic transitions in superconductingSr2VFeAsO3

We have studied a quinary Fe-based superconductor Sr$_2$VFeAsO$_3$ by the measurements of x-ray diffraction, x-ray absorption, M\"{o}ssbauer spectrum, resistivity, magnetization and specific heat. This apparently undoped oxyarsenide is shown to be self doped via electron transfer from the V$^{3+}$ ions. We observed successive magnetic transitions within the VO$_2$ layers: an antiferromagnetic transition at 150 K followed by a weak ferromagnetic transition at 55 K. The spin orderings within the VO$_2$ planes are discussed based on mixed valence of V$^{3+}$ and V$^{4+}$.

울릉도 해안지역 염기성암의 자기적 성질 연구

울릉도의 해안지역에서 염기성암 시료에 대하여 X-선 형광 분광 분석, M<TEX>$\ddot{o}$</TEX>ssbauer 분광 분석 및 SQUID 분석으로 물리적 특성을 조사하여 화산암의 화학적 조성과 시료 내에 존재하는 Fe의 원자가 상태와 자기적 성질을 연구하였다. 울릉도 해안지역의 염기성암은 알칼리 장석 계열의 광물들이 주 광물로 구성되어 있으며, 적철석인 hematite(<TEX>${\alpha}-Fe_2O_3$</TEX>)을 포함한 총 Fe 화합물의 중량비는 10.6~14.5 wt%의 범위에 있음을 알 수 있었다. M<TEX>$\ddot{o}$</TEX>ssbauer spectrum과 자기이력 곡선을 조사한 결과로 부터 모든 시료들의 자기적 성질이 hematite(<TEX>${\alpha}-Fe_2O_3$</TEX>)에 의한 강자성을 나타내고 있음을 알 수 있었다. 또한 10 K~350 K 온도 범위에서 외부 자기장인 +1 T를 인가하고 온도에 따른 자기화의 변화를 측정한 결과로부터 41 K~60 K 사이의 온도에서 시료들의 자기전이가 나타나고 있음을 알 수 있었다. Magnetic properties of basic rocks samples distributed in the seaside area of Ulleung island were investigated by means of X-ray fluorescence spectroscopy (XRF), M<TEX>$\ddot{o}$</TEX>ssbauer spectroscopy and SQUID magnetometer. We found that samples were typical basic rock which had the total amount of iron compounds varies from 10.6 wt% to 14.5 wt% depending on the different regions by XRF. The M<TEX>$\ddot{o}$</TEX>ssbauer spectra and magnetic hysteresis behaviors of the samples show ferromagnetic properties due to hematite. Also, temperature dependences of magnetization at applied magnetic field of 1 T for samples show magnetic transitions at 41 K~60 K.

울릉도 해안지역 화산암의 철 화합물에 관한 연구

울릉도의 해안지역에서 채취한 화산암 시료에 대하여 X-선 회절분석 실험, X-선 형광 분광 분석 및 M<TEX>$\ddot{o}$</TEX>ssbauer 분광 분석으로 물리적 특성을 조사하여 화산암의 화학적 조성과 시료 내에 존재하는 Fe의 원자가 상태와 자기적 성질을 연구하였다. X-선 형광분광 분석의 결과로부터 울릉도 해안지역의 화산암은 지역에 따라 적철석인 hematite(<TEX>$\alpha-Fe_2O_3$</TEX>)를 포함한 총 철 화합물의 양이 10.6 w%에서 14.5 w%인 전형적인 염기성암인 것을 알 수 있었다. M<TEX>$\ddot{o}$</TEX>ssbauer 분광 분석 결과로부터 울릉도 해안지역의 모든 시료에서 hematite에 의한 6중선의 공명 흡수선과 다양한 clay mineral에 포함된 <TEX>$Fe^{3+}$</TEX>에 의한 2중선의 공명흡수선이 나타나고 있으며, pyroxene(<TEX>$(Ca,Fe,Mg)_2(SiO_4)_2$</TEX>)과 ilmenite(<TEX>$FeTiO_3$</TEX>) 그리고 olivine(<TEX>$(Mg,Fe)_2SiO_4$</TEX>) 들에 포함되어 있는 <TEX>$Fe^{2+}$</TEX>에 의한 2중선의 공명흡수선들도 나타나고 있음을 알 수 있었다. 또한 모든 시료들에서 철 화합물들이 주로 <TEX>$Fe^{3+}$</TEX>의 산화철 형태로 존재하므로 울릉도 해안지역의 염기성 화산암들은 육상형성 화산암임을 알 수 있다. Fe compounds of volcanic rock samples distributed in the seaside area of Ulleung island were investigated by means of X-ray diffractometry (XRD), X-ray fluorescence spectroscopy (XRF) and M<TEX>$\ddot{o}$</TEX>ssbauer spectroscopy. We found that samples were typical basic rock which had the total amount of iron compounds including hematite (<TEX>$\alpha-Fe_2O_3$</TEX>) varies from 10.6 w% to 14.5 w% depending on the different regions by XRF. The M<TEX>$\ddot{o}$</TEX>ssbauer spectra of the samples were consisted of one sextet due to hemitite and doublets due to <TEX>$Fe^{3+}$</TEX> in various clay mineral and <TEX>$Fe^{2+}$</TEX> in pyroxene <TEX>$(Ca,Fe,Mg)_2(SiO_4)_2$</TEX>, ilmenite (<TEX>$FeTiO_3$</TEX>) and olivine <TEX>$(Mg,Fe)_2SiO_4$</TEX>. The balance state of Fe ions of all samples was chiefly <TEX>$Fe^{3+}$</TEX>, so we could find that the volcanic rocks distributed in the seaside area of Ulleung island were made in inland.

Absence of the hyperfine magnetic field at the Ru site in ferromagnetic rare-earth intermetallics

The M\"{o}ssbauer Effect(ME) is frequently used to investigate magnetically ordered systems. One usually assumes that the magnetic order induces a hyperfine magnetic field, $B_{hyperfine}$, at the ME active site. This is the case in the ruthenates, where the temperature dependence of $B_{hyperfine}$ at $^{99}$Ru sites tracks the temperature dependence of the ferromagnetic or antiferromagnetic order. However this does not happen in the rare-earth intermetallics, GdRu$_2$ and HoRu$_2$. Specific heat, magnetization, magnetic susceptibility, M\"{o}ssbauer effect, and neutron diffraction have been used to study the nature of the magnetic order in these materials. Both materials are found to order ferromagnetically at 82.3 and 15.3 K, respectively. Despite the ferromagnetic order of the rare earth moments in both systems, there is no evidence of a correspondingly large $B_{hyperfine}$ in the M\"{o}ssbauer spectrum at the Ru site. Instead the measured spectra consist of a narrow peak at all temperatures which points to the absence of magnetic order. To understand the surprising absence of a transferred hyperfine magnetic field, we carried out {\it ab initio} calculations which show that spin polarization is present only on the rare-earth site. The electron spin at the Ru sites is effectively unpolarized and, as a result, $B_{hyperfine}$ is very small at those sites. This occurs because the 4$d$ Ru electrons form broad conduction bands rather than localized moments. These 4$d$ conduction bands are polarized in the region of the Fermi energy and mediate the interaction between the localized rare earth moments.

Crystallographic and Magnetic Properties of Li0.7Co0.2Ti0.2V0.2Fe1.7O4Ferrite

This study examined the crystallographic and magnetic properties of vanadium-substituted lithium cobalt titanium ferrite, <TEX>$Li_{0.7}Co_{0.2}Ti_{0.2}V_{0.2}Fe_{1.7}O_4$</TEX>. Ferrite was synthesized using a conventional ceramic method. The samples annealed below <TEX>$1040^{\circ}C$</TEX> showed X-ray diffraction peaks for spinel and other phases. However, the sample annealed above <TEX>$1040^{\circ}C$</TEX> showed a single spinel phase. The lattice constant of the sample was <TEX>$8.351\;{\AA}$</TEX>, which was relatively unaffected by vanadium-substitution. The average grain size after vanadium-substitution was <TEX>$13.90\;{\mu}m$</TEX>, as determined by scanning electron microscopy. The M<TEX>$\ddot{o}$</TEX>ssbauer spectrum could be fitted to two Zeeman sextets, which is the typical spinel ferrite spectra of <TEX>$Fe^{3+}$</TEX> with A and B sites, and one doublet. From the absorption area ratio of the M<TEX>$\ddot{o}$</TEX>ssbauer spectrum, the cation distribution was found to be (<TEX>$Co_{0.2}V_{0.2}Fe_{0.6})[Li_{0.7}Ti_{0.2}Fe_{1.1}]O_4$</TEX>. Vibrating sample magnetometry revealed a saturation magnetization and coercivity of 36.9 emu/g and 88.6 Oe, respectively, which were decreased by vanadium-substitution.

Magnetism， magetostriction， and M?ssbauer effect studies of Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 alloys

The effects of Al substitution for Fe on the structure， the magnetism， the magnetostriction， the anisotropy and the spin reorientation of a series of Tb0.3Dy0.6Pr0.1（Fe1-xAlx）1.95 alloys （x=0.05，0.1，0.15，0.2，0.25，0.3） at room temperature are investigated. It is found that the compositions of Tb0.3Dy0.6Pr0.1（Fe1-xAlx）1.95 substantially retain MgCu2-type C-15 cubic Laves phase structure when xx=0.2 and the mixture phase increases with x increasing. The lattice constants increase linearly， Curie temperature decreases gradually and the coercive force decreases sharply with x increasing. The vibrating sample magnetormeter measurements show that the relationship between magnetization and substitution x is rather ambiguous. The magnetostriction of the Tb0.3Dy0.6Pr0.1（Fe1-xAlx）1.95 alloys decreases drastically with x increasing and the magnetostrictive effect disappears when x&gt;0.15. However， a small amount of Al substitution is beneficial to a decrease in magnetocrystalline anisotropy. The analysis of the Mssbauer spectra indicates that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry with the increase of Al concentration x，namely spin reorientation takes place, thereby leading to the change of macroscopical magnetism and magetostriction.

Effect of interface on microstructure and soft magnetic properties of Fe65Co35 thin films

Bilayer films with Fe65Co35 main layer/underlayer structure were successfully prepared by magnetron sputtering on different underlayers （Co93Fe7 and Fe）. X-ray diffraction （XRD） analysis and magnetic measurements show that Fe65Co35 thin films deposited on different underlayers have different textures. Moreover, the soft magnetic properties of Fe65Co35 thin films with （200） texture are better than that of Fe65Co35 thin films with （110） texture. Investigation of several typical samples by conversion electron Mssbauer spectrum （CEMS） reveals that the vector of magnetization of Fe65Co35 thin films have a little deviation from the film plane, and the deviation from the film plane of Fe65Co35 thin films with （110） texture are bigger than that of Fe65Co35 thin films with （200） texture. Further study exhibits that this phenomenon is caused by the interface anisotropy induced by magnetoelastic anisotropy at the interface between Fe65Co35 thin film and underlayer.

Temperature Dependent Cation Distribution in Tb2Bi1Ga1Fe4O12

In this study, heavy rare earth garnet <TEX>$Tb_2Bi_1Ga_1Fe_4O_{12}$</TEX> powders were fabricated by a sol-gel and vacuum annealing process. The crystal structure was found to be single-phase garnet with a space group of Ia3d. The lattice constant <TEX>$a_0$</TEX> was determined to be 12.465 <TEX>${\AA}$</TEX>. From the analysis of the vibrating sample magnetometer (VSM) hysteresis loop at room temperature, the saturation magnetization and coercivity of the sample are 7.64 emu/g and 229 Oe, respectively. The N<TEX>$\acute{e}$</TEX>el temperature(<TEX>$T_N$</TEX>) was determined to be 525 K. The M<TEX>$\ddot{o}$</TEX>ssbauer spectrum of <TEX>$Tb_2Bi_1Ga_1Fe_4O_{12}$</TEX> at room temperature consists of 2 sets of 6 Lorentzians, which is the pattern of single-phase garnet. From the results of the M<TEX>$\ddot{o}$</TEX>ssbauer spectrum at room temperature, the absorption area ratios of Fe ions on 24d and 16a sites are 74.7% and 25.3%(approximately 3:1), respectively. These results show that all of the non-magnetic Ga atoms occupy the 16a site by a vacuum annealing process. Absorption area ratios of Fe ions are dependent not only on a sintering condition but also on the temperature of the sample. It can then be interpreted that the Ga ion distribution is dependent on the temperature of the sample. The M<TEX>$\ddot{o}$</TEX>ssbauer measurement was carried out in order to investigate the atomic migration in <TEX>$Tb_2Bi_1Ga_1Fe_4O_{12}$</TEX>.

Magnetism and Mssbauer spectra of cyanide-bridged Ni-Fe nano-molecular-magnets

Nanoparticles of Prussian blue analogues Ni3［Fe(CN)6］·8.28H2O have been successfully synthesized by co-precipitation method. The nanoparticles were characterized by elemental analysis, X-ray diffraction, Fourier transform infrared spectrometry and transmission electron microscopy. Magnetic measurement was carried by superconducting quantum interference device magnetometer and the result showed the the transition temperature Tc=22.8K. The interaction between Ni(Ⅱ) and Fe(Ⅲ) was identified to be a kind of ferromagnetic coupling and was clearly explained by molecular orbital theory. The Mssbauer spectra have been used to explain the origin of magnetism.

Magetostriction, spin reorientation and M?ssbauer effect studies of Tb0.3Dy0.7－xPrx(Fe0.9Al0.1)1.95 alloys

The effect of Pr substitution for Dy on the structure, magnetostriction, anisotropy and spin reorientation of a series of Tb0.3Dy0.7-xPrx(Fe0.9Al0.1)1.95 alloys (x=0, 0.1, 0.20, 0.25, 0.30, 0.35) at room temperature has been investigated. It was found that the Tb0.3Dy0.7-xPrx(Fe0.9Al0.1)1.95 substantially retained the MgCu2-type C-15 cubic Laves phase structure for compositions with x≤0.1 and the lattice constant increases slowly with increasing x. The magnetostriction of the Tb0.3Dy0.7-xPrx(Fe0.9Al0.1)1.95 alloys decreases drastically with increasing x and the magnetostrictive effect disappears for x&gt;0.2. However, the magnetostriction shows a slightly bigger value at x=0.1 than the free alloys and is saturated more easily with the magnetic field H, showing that a small amount of Pr substitution is beneficial to the decrease in the magnetocrystalline anisotropy. The spontaneous magnetostriction λ111 increases linearly with incresasing x， whereas the spin reorientation temperature increases first and then decreases rapidly. The analysis of the Mssbauer spectra indicated that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry with the increase in Pr concentration x， namely the spin reorientation. Compared with the Al substitution，the effect of Pr substitution for Dy on the spin reorientation is smaller.

Structure, magnetism and 119Sn M?ssbauer spectral study on intermetallic compound PrMn6Sn6

The intermetallic compound PrMn6Sn6 was prepared by arc-melting and showed a HoFe6Sn6-type (group space: Immm) structure. The compound is ferromagnetic, where the Mn- and Pr-sublattices are ferromagnetically coupled,and has a Curie temperature of 325 K. The 119Sn Mssbauer spectra between 15 and 360 K were measured, and were analyzed by a simplified model according to the eight Sn crystallographic sites with different nearest-neighbors environment, and the corresponding transferred hyperfine fields and the average value dependence on temperature were obtained. The magnetic structure of the two sublattice is discussed.

Mössbauer spectroscopy of Fe-based nanomaterials

X-ray diffraction, magnetic measurements and Mossbauer spectroscopy were used to study magnetic properties and hyperfine interaction parameters of nanocrystalline (< 10 nm) and bulk bcc Fe, Fe90Ge10, and Fe77Al23 alloys. It has been established that nanocrystalline state does not influence the formation of specific saturation magnetization, Curie temperature, isomer shift and hyperfine magnetic field. No additional sextets in Mo ssbauer spectra as well as special features in temperature dependences of a.c. magnetic susceptibility have been found. A slight increase (∼ 20%) of the width of the nanocrystalline Fe Mossbauer spectral lines has been observed.

Structure, spin reorientation and M?ssbauer spectra of Tb0.3Dy0.7(Fe0.9T0.1)1.95 alloys

The effect of T substitution for Fe on the structure, spin reorientation and Mssbauer spectra of a series of Tb0.3Dy0.7(Fe0.9T0.1)1.95 (T=Mn，Fe，Co，B，Al，Ga) alloys at room temperature has been investigated systemically. The X-ray result shows that all samples are single phase having the cubic Laves-phase structure (C15). The analysis of the Mssbauer spectra indicates that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry for Al and Ga substitution, but remains in the ［111］ direction for B, Mn and Co substitution. The hyperfine field decreases slightly for Al and Ga substitution, does not change for B，Mn substitution and increases greatly for Co substitution. With the substitution of all elements but Co, the isomer shift and the quaduple splitting always increase.

M?ssbauer spectra study on phase variation in a high-coercivity FeCrCo alloy

Variation of the coercivity induced by increasing Cr and Co contents and adding inpurities of Mo and Zr in FeCrCo alloys was investigated using Mssbauer spec tra, fransmission electron microscopy, x-ray diffraction, and magnetic measureme nt. A coercivity as high as 76kA/m is obtained, which is one and half times high er than that (40—52kA/m) of the common alloy. Mssbauer spectra shows that the microstructure of the high-coercivity alloy is apparently different from that of the traditional FeCrCo alloy. The alloy is single-phase after solution treat ment, the non-magnetic γ phase, which weakens the magnetic properties, does no t appear. During the thermomagnetic treatment, the atomic distribution is rearra nged, and leads to the formation of the α2 phase, the spinodal struc ture with the two-phase (α1 +α2 ) in the alloy fully forms after step-tempering. It might be beneficial for forming the high coercivity in alloy. Comparied with th e low-coercivity case, more of the α1 phase exist in the spinodal st ructure.