Control of functions of hydrogen absorbing alloys using strong magnetic fields

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(1) The heat of reaction was investigated experimentally for the LaCo_5-H system in zero field and a magnetic field. Under the influence of magnetic field of 12T the heat of reaction was increased by 5%. This value agreed well with the calculation based on the general formulation of magnetothermodynamic effects in chemical reactions. This is the first observation of the magnetic field effect on the heat of reaction.(2) The magnetic properties of LaCo_5 hydrides and deuterides were measured. The βphase LaCo_5 H (D)_<3.4> is recognized as a saturated ferromagnet, like the metal phase LaCo_5. The γ phase LaCo_5H (D)_<3,4> undergoes a metamagnetic transition at a critical field of 35T (hydride) or 38T (deuteride). These magnetic properties are related to the electronic structure. A new method for hydrogen isotope separation was proposed on the basis of a magnetic field effect using LaCo_5 under the magnetic field of 5T at 303K.The deuterium in the gaseous phase was enriched due to the applied magnetic fields.(3) The pressure-composition isotherms for the hydrides and the deuterides of PrCo_5 and CeCo_5 were measured. The isotope effect was discovered for the β_1+γ region of the PrCo_5H (D)_x. The CeCo_5H_x showed three plateau regions up to 5MPa in the temperature range between 237K and 313K.The magnetic field induced change in the equilibrium pressure for the CeCo_5D_x was higher than CeCo_5H_x.(4) Compton profiles were observed for PdH_<0.6> single crystals using high energy x-ray (115keV) at Spring-8.