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A complex temperature dependence of a.c. susceptibility of Y 2 Fe 17 under high pressures together with recent neutron diffraction studies under pressure proved the instability of the collinear ferromagnetic structure and the development of a non-collinear magnetic arrangement of Fe moments in Y 2 Fe 17 . To study the correlation between magnetic structure and volume in more detail we performed compressibility and linear thermal expansion studies under high pressures up to 100 kbar and 10 kbar, respectively. The compressibility in the paramagnetic state s P (above 10 kbar at room temperature) was determined from the Murnaghan equation of state using the X-ray data, \kappa_{P}=0.80\ {\rm Mbar}^{-1} . The linear thermal expansion and compressibility in the ferromagnetic state at low temperatures are highly anisotropic. As a consequence, the c/a ratio decreases with increasing pressure. The magnetic phase diagram of Y 2 Fe 17 compound was compiled up to 20 kbar.

UPtAl exhibits a ferromagnetic ordering of U magnetic moments at temperatures below T C =42.5 K. The magnetic-ordering transition is accompanied by an anomaly in the temperature dependence of electrical resistivity. This allows us to determine the value of Curie temperature from 휌 vs. T data that can be measured at very high pressures, at which reliable magnetization measurements are difficult. We report on resistivity measurements performed on an UPtAl single crystal under hydrostatic pressures p h 8 GPa. It was observed that the initial increase of T C with p becomes gradually reduced for p >2 GPa until the maximum T C value of , 48 K is reached between 4 and 6 GPa that is followed by a progressively developing downturn of the T C ( p ) curve. The latter result is attributed to the approaching collapse of the U 5 f -moment ferromagnetism. Low-temperature resistivity data point to a rapidly reduced magnetic anisotropy at highest pressures.

The effect of pressure on the lattice parameters of R Ni 2 B 2 C ( R = Y, Ho, Er, Tm, Lu) has been measured in order to investigate the relation of T C to axial ratio c/a in the tetragonal lattice or the cohesive properties of these materials. The large anisotropies are observed in the lattice compression curves especially for R =Ho and Tm; the c -axis is more compressible than the a -axis. On the other hand, the anisotropy in the lattice compression is found to be relatively small for R =Y and Lu. The close relation between T C and c/a is pointed out particularly for R =Ho.

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Abstract: The linear thermal expansion, compressibility and magnetostriction of UNiGa have been measured under high pressure. Huge anisotropic behaviors are observed in these physical quantities. The linear thermal expansion coefficients are α a ∼ 16·10−6 K−1 along thea-axis anda c ∼5·10−6 K−1 along thec-axis, and the linear compressibilities at room temperature are κ a ∼ 3.6·10−3 GPa−1 and κ c ∼ 1.7·10−3 GPa−1 alonga-axis andc-axes, respectively. UNiGa orders antiferromagnetically belowT N=39 K and shows a metamagnetic transition at 4.2 K in magnetic fieldB C=1 T. It is found thatT N decreases andB C increases with increasing pressure.

High‐pressure apparatus for Compton scattering experiments has been developed to study the momentum distribution of conduction electrons in metals and alloys at high pressure. This apparatus was applied to observe the Compton profile of metallic Li under pressure. It was found that the Compton profile at high pressure could be obtained within several hours by using this apparatus and synchrotron radiation. The result on the pressure dependence of the Fermi momentum of Li obtained here is in good agreement with that predicted from the free‐electron model.

The magnetoresistance (MR) of Fe/Cr, Co/Cu and Fe/Cu magnetic superlattices (SL) has been measured at 4.2 K under high pressure up to 2 GPa. It is found that MR of magnetic SL decreases with increasing pressure but different behaviour is observed between Fe/Cr and Fe/Cu or Co/Cu SL. Such a difference is also found in the pressure dependence of the saturation field Hs. The origin of the difference is discussed briefly.