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The effect of high pressure and ion beam irradiation on the magnitude of giant magnetoresistance (GMR) of Fe/Cr magnetic multilayers (MML), [\Fe(20~\ Å )/\Cr(t~\ Å )]20 (abbreviated as \Fe/Cr(t)), has been measured at 77.4 K. It is found that the GMR of Fe/Cr(8) is decreased but that of Fe/Cr(30) is increased by applying pressure. By ion beam irradiation, the electrical resistance of these MMLs is increased significantly and the magnitude of GMR is decreased. Furthermore we have measured the GMR of irradiated Fe/Cr(8) and Fe/Cr(30) under high pressure and compared the results with the sample before irradiation. The GMR of Fe/Cr(8) after the irradiation is found to increase with pressure and the pressure-coefficient of the saturation resistivity is extremely large. These results are discussed on the basis of the spin dependent scattering by the roughness at the interfaces and also bulk scattering in MML in connection with an irradiation-induced instability of the electronic states in Fe/Cr(8). [ABSTRACT FROM PUBLISHER]

Electrical resistivities of double perovskite oxides Sr2Fe(W1-xMox)O6 have been measured at high pressure and high magnetic field to elucidate the transport properties of these materials. It is found that the main mechanism of the transport in the semiconducting phase is variable range hopping conduction and the insulating properties are suppressed by high pressure to show a crossover to metallic state. The magnetoresistances of these oxides are revealed to decrease at high pressure above 1 GPa. Extremely large Grüneisen parameters are found near x = 0.2, where the metal-insulator transition occurs. The origin for these properties will be briefly discussed in connection with the phase diagram. [ABSTRACT FROM AUTHOR]

Abstract: The electrical resistivity and magnetoresistance (MR) of single crystalline -Ce have been measured under high pressure and low temperature. It is found that the temperature dependence of resistivity at low temperature is described as below 10 K, where is the residual resistivity and A is the constant. A decreases significantly as pressure increases, which corresponds to the increase of Kondo temperature at high pressure. A seems to be divergent from higher pressures toward 0.3 GPa, which suggests the existence of magnetic phase boundary. MR ratio of -Ce is positive and enhanced by applying pressure. These results are discussed on the basis of theoretical model presented by Kawakami–Okiji. [Copyright &y& Elsevier]

Abstract: The thermal expansion coefficients of Kondo compounds, CeBe13 and CeRh2Si2, and the magnetostriction of Tb0.3Dy0.7Fe2(Terfenol-D) have been measured at high pressure. By simple analysis using thermodynamical relation, it is found that the density of state at the Fermi level and the Grüneisen parameters of the Kondo compounds decrease rapidly with increasing pressure corresponding to the large pressure-induced enhancement of Kondo temperatures. An anomalous behaviour in the thermal expansion coefficients of CeRh2Si2 is observed at high pressure above . This anomaly is suggested as an origin of pressure-induced superconductivity. The giant magnetostriction (GMS) of Terfenol-D is found to be enhanced by applying hydrostatic pressure below 0.5 GPa but GMS decreases above it. These results are discussed briefly by comparing with the previous ones. [Copyright &y& Elsevier]

Abstract: The thermal expansion and lattice constants of perovskite have been measured at high pressure. It is found that an anomalous expansion due to metal–insulator transition appeared on heating in the temperature dependence of the thermal expansion and its magnitude decreases with increasing pressure. The metal–insulator transition temperature, , increases with increasing pressure. The lattice constants, a, b, and c are found to decrease with increasing pressure but there is a large anisotropy in the lattice compression. The linear com are extracted to be 1.5, 1.9 and for a, b and c-axis, respectively. [Copyright &y& Elsevier]

Abstract: We have attempted to grow single crystals of Ce–Ni–Ge ternary system having layered structure. Several polycrystalline samples, CeNiGe x (), Ce3Ni x Ge y () and Ce2NiGe6, were prepared by an arc-melting of constituent elements. All samples grown by the Czochralsky method are found to contain the phase of the orthorhombic CeNiGe2 type structure. A Rietveld method was applied to analyze the crystal structure of CeNiGe2.2 using X-ray powder diffraction data at room temperature. The refined lattice parameters were  Å,  Å and  Å with the space group Cmmm. The temperature dependence of magnetic susceptibility shows a significant variation in the magnetic properties depending on the concentration of Ge, that is, magnetic phase transition temperature depends on starting materials. It may come from the fact that the magnetic property relies on a structural homogeneity and a stoichiometry. [Copyright &y& Elsevier]

The electrical resistance and the magnetoresistance (MR) in Fe/Cr multilayers have been measured at high pressure. It is found that the effect of pressure on the MR ratio and saturation field (Hs) was significant and the spin-dependent scattering plays an important role in the pressure dependence of MR ratio. The pressure change of Hs is suggested to be dominated by the change in the value on |J| at high pressure. [Copyright &y& Elsevier]

The electrical resistivity of single crystalline HoNi[sub 2]B[sub 2]C has been measured at high pressure and magnetic fields. The three anomalies in the magnetoresistance due to metamagnetic transitions are observed both at ambient and high pressures. It is found that the metamagnetic transition fields increase with increasing pressure. The temperature dependence of electrical resistivity is strongly dependent on magnetic field. Non Fermi liquid behavior is observed near the metamagnetic transition fields. But the normal Fermi liquid behavior recovers after completing the phase transition. The Grüneisen parameters are also calculated to examine the stability of electronic state. [ABSTRACT FROM AUTHOR]

Abstract: The effects of pressure on the magnetization (M) and the magnetostriction (MS) for DyB6 single crystal have been measured at 4.2K. It is found that the M loops are insensitive to pressure, whereas the large MS with magnitude of 0.5% at 5T at ambient pressure is rapidly suppressed by applying pressure. The metamagnetic transition field H M in the M curve increases slightly by applying pressure with the rate of increase, ∂ln H M/∂P, of 0.03GPa−1, which is almost the same value as that for T N, 0.04GPa−1. [Copyright &y& Elsevier]

Abstract: The electrical resistivity of SrFeWMoO has been measured under high pressure in order to make the transport properties of this compound clear. The resistivity decreased with increasing pressure and the magnitude of pressure coefficient below 1GPa is larger than that above 1GPa. It is found that the electrical resistivity shows a temperature dependence, which implies that the conduction of electrons is mainly dominated by a variable range hopping. The coefficient of is decreased by applying pressure and is different between, below and above 1GPa. These results suggest that a kind of phase transition or crossover occurs around 1GPa. [Copyright &y& Elsevier]

Abstract: The electrical resistivity of single crystalline has been measured at high pressure up to 6GPa. It is found that the heavy fermion state becomes unstable at around 2.8GPa, where the coefficient of dependence diverges and the Kondo temperature is 0. This fact indicates the occurrence of quantum phase transition near 2.8GPa. The result will be discussed in connection with the disappearance of the antiferromagnetic ordering temperature near 3GPa. [Copyright &y& Elsevier]

Abstract: The compounds are well known to show a large magnetoresistance (MR) near the M–I phase boundary . The magnetoresistance and AC susceptibility of , which is on the border of M–I phase boundary, have been measured under high pressure. The MR decreases with increasing pressure, especially, at low field of around 2T. The Curie temperature, , is obtained by the temperature dependence of AC susceptibility. is found to increase with pressure with a rate of . [Copyright &y& Elsevier]

Temperature dependence of the electrical resistivity has been measured below 50 K for the sputtered magnetic multilayers [Co(1.02 nm)/Cu(tCu nm)]25 with different Cu thickness at various magnetic fields. It is found that the electrical resistivities of ferromagnetic (FM) multilayer (tCu=0.76 nm) and the antiferromagnetic (AFM) one (tCu=1.05 nm) show temperature dependence of T3/2 and T2, respectively. The slope, A′, of each power law has a maximum near Hs. The results imply that the magnetic fluctuation is a maximum near Hs showing quantum phase transition. [Copyright &y& Elsevier]

Abstract: The electrical resistivity of ordered has been observed at high pressure up to 15GPa. Above 4.5GPa, dependence in the temperature dependent electrical resistivity is observed. The coefficients are found to increase with pressure and show a divergence near 16GPa. This result indicates a quantum critical point near 16GPa. [Copyright &y& Elsevier]

The effect of hydrostatic pressure on the viability of soil microorganisms has been examined to develop a new method of sterilization without using agricultural chemicals and to explore the habitable zone of the microorganisms in the earth's interior. It is found that almost all microorganisms in soil cannot survive above 0.75 GPa at room temperature but a small amount of microorganisms are still alive above 0.75 GPa. The slow rate of releasing pressure is found to have a small effect on the viability. [ABSTRACT FROM AUTHOR]

The magnetoresistances (MRs) of Cr and Cr0.985V0.015 (Cr-V) alloy have been measured at high pressures up to 2.0 GPa in order to elucidate the relation between the transport properties and spin density wave (SDW) antiferromagnetic state. The resistance of Cr is found to increase with increasing magnetic field (H). MR ratios of Cr and Cr-V alloy at room temperature are nearly 0% and 0.3% at 7 T, respectively. But at 77 K, these are 70% and 30% at 7 T at ambient pressure, respectively. MR ratio of Cr at 77 K is found to show a peak ∼1.3 GPa but that of Cr-V alloy decreases smoothly with pressure. The origins of the pressure dependence in the magnitude of MR are discussed in connection with the SDW antiferromagnetic states. [ABSTRACT FROM AUTHOR]

The magnetoresistance (MR) in Fe/Cr magnetic multilayers (MML) has been measured under high pressure up to 2.5 GPa. It is found that the spin-dependent scattering plays an important role in the pressure dependence of MR ratio. In the present work, for [Fe(20 Å)/Cr(10 Å)]20 MML with antiferromagnetic (AF) state, the pressure coefficient of saturation field Hs is (1/Hs)(∂Hs/∂P) = 3.3 × 10-2 GPa-1 between 0.1 and 2.5 GPa. We found that the (1/∣J∣)(∂∣J∣/∂P) for AF-Fe/Cr MML with polycrystalline structure is opposite in sign to that with epitaxial one. For [Fe(20 Å)/Cr(22 Å)]20 MML with ferromagnetic (F) state, anisotropic magnetoresistance (AMR) decreases with increasing pressure. It is suggested that the anisotropy constant decreases with weakening spin-orbit interaction at high pressure. At high field, the AMR is easily suppressed by applying pressure while the giant magnetoresistance around Hs increases slightly with increasing pressure for polycrystalline Fe/Cr MML. [ABSTRACT FROM AUTHOR]

Abstract: The electrical resistance of a single crystal of HoNi2B2C has been measured as a function of temperature (T) and magnetic field (H) under high pressure (P). As pressure increases, decreases with the rate of  K/GPa but increases with  K/GPa. This implies that the superconductivity above competes with antiferromagnetism. The re-entrant superconducting temperature coexisting with the antiferromagnetic phase is increased by applying pressure. The present result indicates that coincides with near 3.2 GPa. [Copyright &y& Elsevier]

Applied hydrostatic pressure dependence of tunneling magnetoresistance (TMR) properties was investigated in magnetic tunnel junctions using the half-metallic Heusler alloy Co2MnSi (CMS). The half-metallic electronic structure in CMS was observed by measuring tunneling-conductance spectroscopy under different applied pressure. The effect of tetragonal distortion in CMS on the electronic structure was also calculated on the basis of the first-principle density-functional method. The TMR ratio showed no remarkable variation with increasing pressure from ambient to 1.5 GPa. It was clearly found that the valence-band edge of the half-metallic gap moved toward the Fermi level with increasing pressure up to 1.8 GPa. These experimental results showed good qualitative agreement with the theoretical calculation of density of states of CMS at high pressure. [ABSTRACT FROM AUTHOR]

Abstract: We investigated elastic properties of the filled skutterudite compound with heavy lanthanide TbRu4P12 by means of ultrasonic measurements under pressure for the first time. TbRu4P12 undergoes a two successive phase transition from a paramagnetic to an antiferromagnetically ordered phase at , then to another phase transition at . We found that a clear elastic anomaly was observed at the two successive phase transition. Furthermore, it is found that they both show a significant pressure dependence. A steep decrease closely associated with is suppressed significantly, but it hardly shifts by applying the pressure. On the other hand, a slight anomaly associated with is gradually suppressed and shifts to lower temperatures by applying the pressure. We argue the elastic behavior and the possible interpretation in each ordering phase. [Copyright &y& Elsevier]

We report the performance of Ag–Pd–Cu alloy as the material of a pressure cell to carry out specific heat measurements at low temperatures and high magnetic fields. The Ag–Pd–Cu alloy is advantageous to reduce the background due to the nuclear specific heat in the pressure cell growing at low temperatures and high magnetic fields. We prepared 70-20-10 alloy composed of 70 mass % of Ag, 20 mass % of Pd, and 10 mass % of Cu. The maximum hardness over 100 HRB (Rockwell-B scale) is achieved by the heat treatment. The magnetization and susceptibility results show that the alloy includes a small amount of magnetic ions, whose concentration is smaller than that in the Be–Cu alloy. We confirm that the specific heat of a piston cylinder cell made of the 70-20-10 alloy increases smoothly from 0.2 to 9 K and the nuclear specific heat decreases drastically in magnetic field compared to that expected in the Be–Cu alloy. The pressure value in the cell at low temperature increases almost linearly up to P=0.4 GPa, which is nearly the limit of the inner piston made of the 70-20-10 alloy, with increasing of the load applied at room temperature. [ABSTRACT FROM AUTHOR]

The electrical resistivity and magnetoresistance (MR) of CePtSi2 have been measured under high pressure in order to clarify the electronic state around TN ∼ 0 K. ρmag (T) at ambient pressure, defined as ρmag = ρ(CePtSi2)-ρ(LaPtSi2), increases with decreasing temperature until it shows a maximum around 28 K(=T2) and a small shoulder around 5 K(=T1). T1 increases with applying pressure and merges into T2 around 1.0 GPa. T2 is almost constant up to 1.0 GPa, but increases rapidly with applying pressure above 1.0 GPa. Negative MR was observed up to 2.4 GPa at 4.2 K. The magnitudes of MR at 9 T are-24.5% and-7.9% at 0.1 and 2.4 GPa, respectively. By applying the Okiji-Kawakami model to the present results, it is found that the Kondo temperature TK increases with increasing pressure. The slope of pressure dependence of MR ratio at 9 T changes slightly around 1.0 GPa. These results suggest a pressure-induced crossover in the electronic states around 1.0 GPa. [ABSTRACT FROM AUTHOR]

Abstract: The thermal expansion and lattice constants of polycrystalline GdAl2 have been measured under high pressure. It is found that as pressure increases, the Curie temperature increases with a ratio of  K/GPa and the spontaneous volume magnetostriction decreases rapidly. C15 structure is stable up to 12.4 GPa and the bulk modulus is 75.3 GPa at room temperature. Grüneisen parameter of is estimated to be 3.84. Using these experimental results, the pressure dependence of is discussed on the basis of the itinerant electron model of ferromagnetism. [Copyright &y& Elsevier]

Abstract: The influence of pressure on the formation of U magnetic moments and mediation of exchange interactions are two principal aspects of the complex role of the 5f-ligand hybridization in magnetism of U intermetallics. Application of external pressure yields changes of interatomic distances, which are the crucial parameters controlling the hybridization. We report on pressure experiments with a 5f-electron ferromagnet UPtAl (T C=42.5K, M s=1.4 μ B/f.u. at ambient pressure). Application of hydrostatic pressure up to 1GPa yields decrease of the spontaneous magnetization M s with a rate dM s/dp=−0.027 μ B/GPa, whereas T C increases (dT C/dp=2.5K/GPa). Extension of the electrical resistivity measurements of UPtAl to pressures up to 22GPa reveals that the initial increase of T C with pressure continues up to 6GPa, where T C reaches the maximum value, and decreases with further increasing pressure. The drastic change of the R(T) curve at 17GPa is presumably connected with suppression of ferromagnetism in UPtAl. [Copyright &y& Elsevier]

• New phase diagram of ferromagnetic shape memory alloy Ni 2+ x MnGa 1− x. • Characteristic composition dependence of phase transitions related to magnetism and structure. • Comprehensive review that includes other representative Ni-Mn-Ga Heusler alloys. [Display omitted] This study experimentally investigates a series of phase transitions of ferromagnetic shape memory alloys, Ni 2+ x MnGa 1− x , in the composition range 0.02 ≤ x ≤ 0.27. An experimental phase diagram of these alloys was constructed by the use of electrical resistivity, thermomagnetization, and thermoanalysis measurements, and compared with both the Ni-rich Ni 2+ x Mn 1− x Ga and Mn-rich Ni 2 Mn 1+ y Ga 1− y alloy systems which have been extensively studied as proto-materials for ferromagnetic Heusler alloys. The comparison makes it clear that there are remarkable composition dependencies for the following characteristic temperatures. All three systems have the common property that Curie temperature decreases and martensitic transition temperature increases with increasing x till the both temperatures coincide each other. As for the magnetostructural coupling temperature, however, the Ni-rich system has a wide temperature range, and the Mn-rich system does not show signs of the magnetostructural coupling, whereas the magnetostructural coupling was observed in Ni 2+ x MnGa 1− x alloys in the range 0.10 ≤ x ≤ 0.12 which has similar characteristics between the former two systems. The premartensitic transition temperature was also observed in Ni 2+ x MnGa 1− x alloys; it reached the ambient temperature at x = ~0.04, the highest of the three alloy systems. In addition, an intermartensitic transition appeared in Ni 2+ x MnGa 1− x alloys in the composition range 0.06 ≤ x ≤ 0.10, which showed a drastic change especially in the electrical resistivity. These characteristic temperatures are also compared in terms of the number of valence electrons among the Ni–Mn–Ga Heusler alloy systems, and the differences are clarified and discussed in detail. [ABSTRACT FROM AUTHOR]

Abstract: We have measured the transverse elastic constant of under hydrostatic pressure of 0.35GPa in the magnetic field up to 12T. The magnetic transition temperature is enhanced by applying pressure in large, while the metal-insulator (M–I) transition temperature increases slightly. These behaviors are very consistent with the evaluation of Grüneisen parameters by using the thermodynamic relation. The order parameter for the M–I transition was discussed on the basis of this pressure experiment. [Copyright &y& Elsevier]

Ferromagnetic epitaxial B2-type Fe3Si/FeSi2 superlattices were prepared on Si(111) at room temperature by facing target direct-current sputtering. The bilinear and biquadratic coupling constants J1 and J2 of the antiferromagnetically coupled superlattice were comparable to those of the similar superlattices using Fe layers although the saturation magnetization of Fe3Si is approximately half as large as that of Fe. The authors believe that this is due to the formation of a well-ordered quantum well in the spacers, which is mainly caused by the regular accumulation of highly oriented Fe3Si layers. [ABSTRACT FROM AUTHOR]

Abstract: To elucidate microscopically the transformation from the Fermi liquid to non-Fermi liquid states of an antiferromagnetic (AFM) Kondo compound CeAl2, we have carried out AC- and 27Al-NQR measurements at pressures up to . The AFM transition temperature is suppressed from 3.8 to (2.4GPa), and the NQR spectrum in the AFM ordered state varies in shape from a complex structure at with large linewidth to a Lorentzian-like structure with . This is ascribed to the transformation from a mixing-phase of the incommensurate and commensurate orderings at to a single phase of commensurate above . Variations in the spin–lattice relaxation behavior of 27Al with pressure indicate the increase of the itinerant electron character and the density of states at the Fermi level. [Copyright &y& Elsevier]

The electrical resistivities of Fe72(NixPt1-x)28 alloys at high pressure have been measured as a function of temperature T(K) in the range of 77.4. The main result is that Martensitic transition temperature TM and Curie temperature Tc in x=0.2 decreased with increasing pressure. The pressure derivatives are dTc/dP=-85.7 K/GPa and dTM/dP=-37.8 K/GPa. From this result, it is suggested that TM becomes to be the same as Tc under high pressure. [Copyright &y& Elsevier]

The electrical resistivity of single crystalline CeRh2Si2 has been measured in the temperature range from 2.0 to 300 K under high pressure up to 2.3 GPa. The coefficient of T2 term A(P) and the residual resistivity ρ0(P) have been obtained as a function of pressure. It is found that A(P) shows one maximum and ρ0(P) show two maxima near the pressure where the magnetic ordering phases disappear. The result is discussed on the basis of pressure-induced quantum phase transition. [Copyright &y& Elsevier]

A correction is presented for the article "Interlayer coupling in ferromagnetic epitaxial Fe3Si/FeSi2 superlattices," in a 2006 issue of "Applied Physics Letters."

Abstract: We investigated the elastic properties of the filled skutterudite compound under hydrostatic pressures. Elastic softening above the metal–insulator transition is enhanced by applying pressures, especially in the transverse elastic constant . The enhanced elastic softening suggests quadrupole moment may be one of the possible ordering parameters below . Strangely, the softening is not a monotonic evolution with respect to pressure; the strongest softening is observed under pressure of in . Jahn–Teller energy and quadrupolar interaction also display anomalies around this pressure. This experimental fact suggests a strong interplay between the metal–insulator transition and the subsequent magnetic phase transition in . [Copyright &y& Elsevier]