Electronic conduction in GaM4Se8 (M=Nb,Ta) compounds with the fcc GaMo4S8-type structure originates from hopping of localized unpaired electrons (S=1 / 2) among widely separated tetrahedral M4 metal clusters. We show that under pressure these systems transform Mott insulators to a metallic and superconducting state T(C)=2.9 5.8 K at 13 11.5 GPa for GaNb4Se8 GaTa4Se8, respectively. The occurrence superconductivity is shown be connected pressure-induced decrease MSe6 octahedral distortion...

We have investigated the effect of pressure on electronic, magnetic, and structural properties a single crystal conducting, ferromagnet ${(T}_{C}=157\mathrm{K})$ ${\mathrm{La}}_{0.82}{\mathrm{Sr}}_{0.18}{\mathrm{CoO}}_{3}$ located near boundary metal-insulator transition. Contrary to results reported related systems, we find transition from conducting state an insulating decrease ${T}_{C}$ with increasing while lattice structure remains unchanged. show that this unusual behavior is driven by...

The crystal structures of the tetrahedral cluster compounds GaNb(4)S(8) and GaTa(4)Se(8) were determined by single-crystal X-ray diffraction. They crystallize in cubic GaMo(4)S(8) structure type (F3m), which can be derived from spinel shifting metal atoms off centers chalcogen octahedra along [111]. Electrical resistivity magnetic susceptibility measurements show that electronic conduction originates hopping localized unpaired electrons (S = (1)/(2)) among widely separated Nb(4) or Ta(4)...

High-pressure $^{149}\mathrm{Sm}$ nuclear forward scattering of synchrotron radiation and specific heat measurements have been performed on the intermediate valent Kondo insulator ${\mathrm{SmB}}_{6}$. The results show that at a critical pressure ${p}_{c}\ensuremath{\approx}6\text{ }\text{ }\mathrm{GPa}$, where charge gap closes, first order transition occurs to magnetically ordered state, which shows typical features trivalent samarium compounds. similarity with SmS stresses role local...

Antiferromagnetism in ${\mathrm{EuCo}}_{2}{\mathrm{P}}_{2}$ ( ${\mathrm{ThCr}}_{2}{\mathrm{Si}}_{2}$-type structure) is due to ordering of the ${\mathrm{Eu}}^{2+}(^{8}S_{7/2})$ sublattice moments $({T}_{N}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}66.5\mathrm{K})$ while $\mathrm{Co}(3d)$ does not carry any magnetic moment. undergoes a pressure-induced isostructural phase transition at ${p}_{c}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3.1\mathrm{GPa}$. ${}^{151}$Eu...

The intermetallic compound ${\mathrm{YbCu}}_{2}{\mathrm{Si}}_{2}$ is a well-known nonmagnetic (NM) Yb intermediate-valent with valence of 2.9 at ambient pressure and 300 K. In the present work we have investigated effect high on ground state properties both microscopic macroscopic levels by using ${}^{170}\mathrm{Yb}$ M\"ossbauer effect, electrical resistance, x-ray diffraction techniques, respectively. High-pressure data indicate that lattice structure stable up to 22.2 GPa. value bulk...

Compounds from the solid solution ${\mathrm{Eu}}_{y}{\mathrm{Fe}}_{4\ensuremath{-}x}{\mathrm{Co}}_{x}{\mathrm{Sb}}_{12}$ were synthesized and found to crystallize in partially filled skutterudite-type structure ${\mathrm{LaFe}}_{4}{\mathrm{P}}_{12}.$ The maximal Eu content gradually decreases practically full occupancy $y=0.83$ ${\mathrm{Eu}}_{0.83}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ $y=0.44$ for ${\mathrm{Eu}}_{0.44}{\mathrm{Co}}_{4}{\mathrm{Sb}}_{12}.$ As a function of Fe/Co substitution...

We report the first observation of a pressure-induced breakdown magnetically ordering ${\mathrm{Eu}}^{2+}$ ($J=\frac{7}{2}$) state to nonmagnetic intermediate-valent in antiferromagnetically ordered Eu(${\mathrm{Pd}}_{0.8}$${\mathrm{Au}}_{0.2}$)$_{2}\mathrm{Si}_{2}$. The experimental results allow us determine limits range Eu mean valence $2.0<~\overline{v}<~2.2$ at 4.2 K, over which magnetic order and intermediate can coexist.

${\mathrm{Eu}}_{0.83}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12},$ was synthesized by arc melting in homogeneous practically single phase form. From Rietveld refinement isotypism derived with the ${\mathrm{LaFe}}_{4}{\mathrm{P}}_{12}$-(skutterudite)-type, space group $\mathrm{Im}3\ifmmode\bar\else\textasciimacron\fi{},$ No. 204. The also served to determine Eu content of $x=0.83(2).$ ${\mathrm{Eu}}_{0.83}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ orders magnetically below 84 K and isothermal magnetization...

High pressure measurements on the nonmagnetic (NM) heavy fermion (HF) compound ${\mathrm{Yb}}_{2}{\mathrm{Ni}}_{2}\mathrm{Al}$ using ${}^{170}\mathrm{Yb}$ M\"ossbauer effect, electrical resistance, and x-ray diffraction techniques reveal for $p>8\phantom{\rule{0ex}{0ex}}\mathrm{GPa}$ below 2 K a crossover from NM HF state to magnetically ordered of $\mathrm{Yb}(4f)$ local moments $({\ensuremath{\mu}}_{\mathrm{Yb}}\ensuremath{\approx}1{\ensuremath{\mu}}_{B}$ at 1.8 9 GPa). This is not...

$^{57}\mathrm{Fe}$ nuclear forward scattering on the chiral magnet FeGe reveals an extremely large precursor phase region above helimagnetic ordering temperature ${T}_{C}(p)$ and beyond pressure-induced quantum transition at 19 GPa. The decrease of magnetic hyperfine field $⟨{B}_{\text{hf}}⟩$ with pressure is accompanied by a increase width distribution $⟨{B}_{\text{hf}}⟩$, indicating strong quasistatic inhomogeneity states in region. Hyperfine fields order 4 T (equivalent to moment...

The phase transitions of the strongly correlated tetrahedral ${\text{V}}_{4}$-cluster compound ${\text{GeV}}_{4}{\text{S}}_{8}$ have been studied by low-temperature powder x-ray diffraction, magnetic susceptibility, and specific heat measurements. crystal structure is cubic at room temperature (space group $F\overline{4}3m$) transforms to orthorhombic $Imm2$) ${T}_{S}=30\text{ }\text{K}$. A Jahn--Teller distortion reduces symmetry from $\overline{4}3m$ $mm2$. second transition 18 K onset...

In order to probe the changes in valence state and magnetic properties of Eu metal under extreme pressure, x-ray absorption near-edge spectroscopy, circular dichroism, synchrotron M\"ossbauer spectroscopy experiments were carried out. The isomer shift exhibits anomalous pressure dependence, passing through a maximum near 20 GPa. Density functional theory has been applied give insight into pressure-induced both Eu's electronic structure shift. Contrary previous reports, is found remain nearly...

We have investigated inelastic scattering of synchrotron radiation by ${}^{119}\mathrm{Sn}$ nuclei using the radiative channel nuclear deexcitation. The energy dependence 23.8795-keV x rays a $\ensuremath{\beta}$-Sn foil was measured with sub-meV resolution. In conditions experiment incoherent over various and averaged phonon momentum transfer. experimental data are compared theory absorption. general agreement is reasonable, however, some deviation noted. possible origin discrepancy discussed.

Extensive $^{151}\mathrm{Eu}$ M\"ossbauer-effect studies in a wide range of temperatures (700-1.4 K) are reported for the samples Eu${\mathrm{Pd}}_{3}$${\mathrm{B}}_{0.5}$ and Eu${\mathrm{Pd}}_{3}$B. The valence europium, which is trivalent Eu${\mathrm{Pd}}_{3}$, observed to change with boron content. temperature dependence M\"ossbauer spectrum Eu${\mathrm{Pd}}_{3}$B suggests that europium ions undergo charge ordering at low temperature.

The pressure dependence of the $^{57}\mathrm{Fe}$ hyperfine parameters in amorphous and crystalline ${({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Ni}}_{x})}_{3}\mathrm{B}$ alloys ($x=0 \mathrm{and} 0.75$) were measured by M\"ossbauer spectroscopy. A similar response all for both phases with decreasing volume was observed. field indicates that distribution Fe-B interatomic distances is about two times narrower than Fe-Fe x-ray scattering.

We have investigated the effect of pressure on magnetic and structural properties frustrated heavy-fermion antiferromagnet YbAgGe in an extended range up to 20 GPa using electrical resistivity x-ray diffraction, respectively. find that with increasing pressure, ordering temperature $({T}_{m})$ first increases rapidly, passes through a maximum (${T}_{m}=5.4\text{ }\text{K}$ at 6.8 GPa), then drops toward zero for $p$ above 16 GPa, while structure remains unchanged about GPa. attribute...

We have investigated the impact of Ru substitution for Co on behavior ferromagnetic superconductor UCoGe by performing x-ray diffraction, magnetization, specific heat, and electrical resistivity measurements polycrystalline samples ${\mathrm{UCo}}_{1\ensuremath{-}x}{\mathrm{Ru}}_{x}\mathrm{Ge}$ series $(0\ensuremath{\ge}x\ensuremath{\le}0.9)$. The initial up to $x\ensuremath{\approx}0.1$ leads a simultaneous sharp increase Curie temperature spontaneous magnetization maximum values...

The perovskite antiferromagnetic $({T}_{\mathrm{N}}\ensuremath{\sim}220\phantom{\rule{0.28em}{0ex}}\mathrm{K})$ insulator ${\text{EuNiO}}_{3}$ undergoes at ambient pressure a metal-to-insulator transition ${T}_{\mathrm{MI}}\phantom{\rule{0.28em}{0ex}}=\phantom{\rule{0.28em}{0ex}}460\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ which is associated with simultaneous orthorhombic-to-monoclinic distortion, leading to charge disproportionation. We have investigated the change of structural and magnetic...

The phonon density of states (DOS) $\ensuremath{\beta}\ensuremath{-}\mathrm{S}\mathrm{n}$ has been directly determined using nuclear inelastic scattering synchrotron radiation by ${}^{119}\mathrm{Sn}\mathrm{}$ nuclei. obtained DOS is in good agreement with theoretical calculations and provides an accurate estimation the Lamb-M\"ossbauer factor, mean-square displacement atoms lattice contribution to specific heat $\ensuremath{\beta}\ensuremath{-}\mathrm{S}\mathrm{n}.$

From Mossbauer effect, lattice constant and susceptibility measurements we show that Eu is nearly divalent in Eu(Cu,Ag,Au)(P,As,Sb). However, the LIII X-ray absorption spectra consist of a pronounced double structure, suggesting non-integral mean valence. The high-energy structure LIII-edge interpreted as final-state (shake-up) effect. This finding strongly supports existence effects compounds previously reported by Sampathkumaran et al (1985) EuPd2P2.

We have investigated the effect of pressure on electrical transport and magnetic properties ferromagnetic Fe${}_{1\ensuremath{-}x}$Co${}_{x}$Si alloys for $x=0.1$ (${T}_{\mathrm{C}}~11 \mathrm{K}$) $x=0.2$ (${T}_{\mathrm{C}}~32 using resistivity measurements up to about 30 GPa. also studied these samples ($x=0.1$ $x=0.2$) a sample with $x=0.3$ (${T}_{\mathrm{C}}~43 at ambient $^{57}\mathrm{Fe}$ M\"ossbauer-effect (ME) spectroscopy. The ME results indicate that effective hyperfine field...