TRANSFORMATION CHARACTERISTICS OF SINGLE CRYSTAL Mn-Ni-C ALLOYS

Transformation of an Mn85Ni9C6 single crystal has been studied by neutron diffraction, ultrasonic techniques, coldstage microscopy and low temperature X-ray diffraction. An FCC→FCT transformation occurs at 174K (Ms) and although the (Af) is only some 12K (± 3) higher, both forward and reverse transformations are spread over some 70K despite marked lattice softening (C is only 0.27 x 10-10 Nm-2 and the Zenar anistropy parameter equals 36 at the MS), and there is a discontinuous change in both the 'c' axis and the volume, suggesting the presence of a first order transformation. However, in contrast to most alloys which show this transformation, the Mn85Ni9C6 alloy appears to show no discontinuity between the 'a' FCC and the 'a'FCT parameters throughout the region where the two phases co-exist. Two-surface analysis has confirmed that shear traces occur on (110) planes, and metallographic features in general are similar to those observed in in-Tl. The transformation as monitored at the surface shows the same characteristics as found in the bulk material, except that the Ms is higher by 10-20K

An explanation of the 'martensite start' - 'martensite finish' temperature interval

SIGLELD:9091.9F(MPD/NBS--192). / BLDSC - British Library Document Supply CentreGBUnited Kingdo

On the martensitic transformation in fcc manganese alloys V. the accompanying magnetic transition

SIGLEAvailable from British Library Document Supply Centre- DSC:8053.4153(RAL--88-022) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

On the Way to a Gutzwiller Density Functional Theory

Abstract. Multi-band Gutzwiller-correlated wave functions reconcile the contrasting concepts of itinerant band electrons versus electrons localized in partially filled atomic shells. The exact evaluation of these variational ground states in the limit of large coordination number allows the identification of quasi-particle band structures, and the calculation of a variational spinwave dispersion. The study of a generic two-band model elucidates the co-operation of the Coulomb repulsion and the Hund’s-rule exchange for itinerant ferromagnetism. We present results of calculations for ferromagnetic nickel, using a realistic 18 spin-orbital basis of 4s, 4p and 3d valence electrons. The quasiparticle energy bands agree much better with the photo-emission and Fermi surface data than the band structure obtained from spin-density functional theory (SDFT). 1 Exchange versus Correlations More than 50 years ago two basically different scenarios had emerged from early quantum-mechanical considerations on electrons in metals with partly filled d bands. Scenario I: As proposed by Slater [1] and Stoner [2], band theory alone wa