Smaller Bulk Modulus Research Articles

Magnetic contribution to the bulk modulus of 3d transition metals and alloys

Experimental data on the bulk modulus of 3d transition metals and alloys are summarized. An intrinsic magnetic contribution caused by the existence of a local magnetic moment has been estimated from the difference in bulk modulus between the ferromagnetic state and paramagnetic state of Fe 65Ni 35 Invar alloy. The anomalously small bulk modulus in 3d transition metals and alloys can be well understood in terms of the magnetic contributions provided a quadratic dependence on the amplitude of local magnetic moments of the magnetic energy.

Bulk modulus and martensitic transformation in Mn-Cu alloys

The concentration dependence of elastic moduli has been measured over a wide concentration range of Mn-Cu alloys by means of neutron inelastic scattering and ultrasonic measurements. The elastic constant C 11 markedly decreases with the increase of Mn content and attains its minimum value near the composition Mn 82Cu 18 at which the martensitic transformation takes place at room temperature. However, a direct trigger of the phase transition is attributed to the vanishing of the shear modulus, contrary to our previous results of neutron inelastic scattering. An anomalous volume effect is discussed in connection with the small bulk modulus near the martensitic transformation in γ-MnCu alloys. The possibilities of d-electron Coulomb correlation and the formation of the local magnetic moment are discussed as origins of the martensitic transformation in Mn-rich Mn-Cu alloys.

Compressibilities and volume dependence of Tcfor eleven Chevrel phase superconductors

Compressibility measurements up to 29.8 kbar (10 kbar=1 GPa) are presented for a number of superconducting ternary molybdenum sulphides and selenides as well as the binary compound Mo6Se8. The percent volume change ( Delta V/V0) exhibits a strong nonlinear dependence on applied pressure. Values of the bulk modulus (B0) and its first pressure derivative (B0') are obtained by fitting these data to the Murnaghan equation of state. This analysis reveals a small bulk modulus for each material, with values comparable to those found in simple s-p elements such as indium. The data are also utilised to convert previously measured pressure effects on the superconducting transition temperature into the more physically meaningful volume dependence of Tc.