arXiv subjects

S. Ostanin

Publications and source records attributed to S. Ostanin.

22 records · Page 2Linked to original sources

arXiv2003

The easy axis of the magnetic response of the conduction electrons of yttrium and rare earths

We describe a scheme for first-principles calculations of the static, paramagnetic, spin susceptibility of metals with relativistic effects such as spin-orbit coupling included. This gives the direction for an applied modulated magnetic field to maximise its response. This easy axis depends on the modulation's wave-vector q. For h.c.p. yttrium we find the peak response at a q= (0,0,0.57)pi/c, coincident with a Fermi surface nesting vector, to have an easy axis perpendicular to q. This is consistent with the {\it helical} anti-ferromagnetic order found in many dilute rare earth-Yalloys. Conversely, the easy axis for the response to a uniform magnetic field lies along the c-axis. The conduction electrons' role in the canting of magnetic moments in Gd-Y alloys and other rare earth materials is mooted.

cond-mat.mtrl-sci↗

arXiv2003

Effect of point defects on heat capacity of yttria-stabilized zirconia

First-principles calculation and anharmonic dynamical theory were used in sequence to explain a large excess heat capacity observed in yttria-stabilized zirconia in comparison with the additive rule value. It is found that the excessive shape of heat capacity decays gradually with the Y$_{2}$O$_{3}$ doping when the number of environmentally different O sites falls to its zero value at 33 mol % Y$_{2}$O$_{3}$-ZrO$_2$ due to the Y atoms adjacent. The model and results presented in this work provide a key insight into the complex behaviour and characterization of fast-ion conductors.

cond-mat.mtrl-sci↗

arXiv2003

A density functional study of pressure induced superconductivity in P and its implication for spintronics

The stability of high-pressure phases of P has been studied using density functional theory and the local density approximation. Using a linear response technique, we have calculated the phonon spectrum and electron-phonon interaction for bcc P and predict it to be superconducting with $T_c$ of 19 K. We propose that this phase might be realized in epitaxial thin films using templates such as V(100), Fe(100) or Cr(100) relevant to spintronics applications.

cond-mat.supr-con↗

arXiv2002

Anisotropic and incommensurate spin fluctuations in hcp iron and some other nearly magnetic metals

We present an ab initio theoretical formalism for the static paramagnetic spin susceptibility of metals at finite temperatures. Since relativistic effects, e.g. spin-orbit coupling, are included, we can identify the anisotropy or easy axes of the spin fluctuations. Our calculations find hcp-iron to be unstable to in ab-plane, incommensurate anti-ferromagnetic (AFM) modes (linked to nested Fermi surface) below T_N =69K for the lowest pressures under which it is stable. T_N swiftly drops to zero as the pressure is increased. The calculated susceptibility of yttrium is consistent with the helical, incommensurate AFM order found in many rare-earth-dilute yttrium alloys. Lastly, in line with experimental data, we find the easy axes of the incommensurate AFM and ferromagnetic spin fluctuations of the normal state of the triplet superconductor Sr2RuO4 to be perpendicular and parallel with the crystal c-axis resepctively.

cond-mat.mtrl-sci↗