Effect of the susceptibility on the magnetic phase diagrams of a ferrimagnet with magnetic instability

The magnetic phase diagrams of a two-sublattice ferrimagnet with a magnetically unstable subsystem are calculated taking account of the susceptibility. Analytic expressions are obtained for the phase-transition fields and critical values of the parameters of the ferrimagnet. The evolution of the magnetic phase diagrams as the susceptibility of the unstable sublattice increases is analyzed.     

Neutron diffraction study of magnetic properties of TmCo2

The present neutron diffraction studies have confirmed that TmCo₂ represents an exception within the RCo₂ series. It was found that, in contrast with other heavy RCo₂ compounds, the Co sublattice in TmCo₂ does not order magnetically below the Curie temperature (T_c = 3.9 K). This is assumed to be due the fact that in TmCo₂ the intersublattice (f-d) molecular field is smaller than the critical field necessary to induce magnetic order within the Co sublattice, as is the case in other RCo₂ compounds. Furthermore, we show that the magnetic structure and the onset of long-range order in TmCo₂ depend sensitively on the sample preparation, which partly explains the differing results published earlier.     

Investigation of some parametric convex programming problems

Translated from Optimal'nost Upravlyaemykh Dinamicheskikh Sistem, No. 19, pp. 20–29, Vsesoyuznyi Nauchno-Issledovatel'skii Institut Sistemnykh Issledovanii, Moscow (1988).     

Information and Distinguishability of Ensembles of Identical Quantum States

We consider a fixed quantum measurement performed over n identical copies of quantum states. Using a rigorous notion of distinguishability based on Shannon’s 12th theorem, we show that in the case of a single qubit, the number of distinguishable states is , where (α₁,α₂) is the angle interval from which the states are chosen. In the general case of an N-dimensional Hilbert space and an area Ω of the domain on the unit sphere from which the states are chosen, the number of distinguishable states is . The optimal distribution is uniform over the domain in Cartesian coordinates.     

Eigenvalues of a One-Dimensional Dirac Operator Pencil

We study the spectrum of a one-dimensional Dirac operator pencil, with a coupling constant in front of the potential considered as the spectral parameter. Motivated by recent investigations of graphene waveguides, we focus on the values of the coupling constant for which the kernel of the Dirac operator contains a non-trivial square integrable function. In physics literature such a function is called a confined zero mode. Several results on the asymptotic distribution of coupling constants giving rise to zero modes are obtained. In particular, we show that this distribution depends in a subtle way on the sign variation and the presence of gaps in the potential. Surprisingly, it also depends on the arithmetic properties of certain quantities determined by the potential. We further observe that variable sign potentials may produce complex eigenvalues of the operator pencil. Some examples and numerical calculations illustrating these phenomena are presented.     

Magnetic properties of the HoMn2Ge2 intermetallic compound

The magnetic properties of a tetragonal intermetallic compound, namely, HoMn₂Ge₂, are investigated experimentally and theoretically. The experimental temperature dependences of the initial magnetic susceptibility and the lattice parameters are obtained in alternating and static magnetic fields. The magnetization curves are measured in strong magnetic fields up to 50 T. The parameters of the crystal field and Ho-Mn and Mn-Mn exchange interactions are determined, and the temperature dependence of the magnetic field of the phase transition from an antiferromagnetic phase to a ferromagnetic phase in a magnetic field aligned along the tetragonal axis is calculated.     

The structure and fatigue life of titanium alloys processed by electrical pulses

The structure and properties of VT3-1 titanium alloy processed by electrical pulses are investigated. The electric pulse processing improves the fatigue life of titanium specimens, as follows from high-cycle fatigue tests.