Magnetic structure and phase diagram of TmB4

Magnetic structure of single crystalline TmB4 has been studied by magnetization, magnetoresistivity and specific heat measurements. A complex phase diagram with different antiferromagnetic (AF) phases was observed below TN1 = 11.7 K. Besides the plateau at half-saturated magnetization (1/2 MS), also plateaus at 1/9, 1/8 and 1/7 of MS were observed as function of applied magnetic field B//c. From additional neutron scattering experiments on TmB4, we suppose that those plateaus arise from a stripe structure which appears to be coherent domain boundaries between AF ordered blocks of 7 or 9 lattice constants. The received results suggest that the frustration among the Tm3+ magnetic ions, which maps to a geometrically frustrated Shastry-Sutherland lattice lead to strong competition between AF and ferromagnetic (FM) order. Thus, stripe structures in intermediate field appear to be the best way to minimize the magnetostatic energy against other magnetic interactions between the Tm ions combined with very strong Ising anisotropy.Comment: 4 pages, 4 figures, conference contribution - CSMAG 0

Transport properties of HoB12

Abstract. We present measurements of the electrical resistivity of single crystalline HoB12 down to a temperature of 1.6 K and in magnetic fields up to 6 T. The obtained results confirm the previous investigation of the magnetic phase diagram by magnetization and specific heat measurements of this compound. The spin wave scattering of conduction electrons and spin disorder resistivity in the antiferromagnetic and in the paramagnetic phase, respectively, are analyzed. Keywords HoB12, electrical resistivity, magnetic phase diagram. PACS 72.15.Eb, 75.50.E

Evolution of phases in Al55Ni30Pd15\mathrm{Al_{55}Ni_{30}Pd_{15}} alloy at temperatures up to 600 °C

The originally as-cast Al55Ni30Pd15 alloy was investigated during continuous heating from room temperature to 600 °C and after annealing at 600 °C for respective 455, 2650, and 4050 h. In the investigation the synchrotron X-ray diffraction and the high-resolution scanning electron microscopy inclusive of the energy-dispersive X-ray spectroscopy were used. In all the investigated conditions β-(Ni,Pd)Al (Pm3m) and Al3(NiPd)2 (P3m1) phases were identified. After 2650 h of annealing the former phase was found to be separated into two isostructural modifications differing from one another in Pd- and Ni-contents. The annealing for 455 h contributed to the decrease of lattice parameters in the Al3NiPd phase compared to the original as-cast condition

Fractional magnetization plateaus and magnetic order in the Shastry Sutherland magnet TmB4

We investigate the phase diagram of TmB4, an Ising magnet on a frustrated Shastry-Sutherland lattice by neutron diffraction and magnetization experiments. At low temperature we find Neel order at low field, ferrimagnetic order at high field and an intermediate phase with magnetization plateaus at fractional values M/Msat = 1/7, 1/8, 1/9 ... and spatial stripe structures. Using an effective S = 1/2 model and its equivalent two-dimensional (2D) fermion gas we suggest that the magnetic properties of TmB4 are related to the fractional quantum Hall effect of a 2D electron gas.Comment: 4 pages, 3 figure

Magnetic Field Influence on the Thermal Conductivity of PrB6PrB_6

Results of thermal conductivity measurements on single crystalline $PrB_6$ sample in the temperature range of 2-30 K and in magnetic field up to 14 T are presented. The obtained results are discussed in order to estimate the electron, phonon, and magnetic contributions to thermal conductivity. Taking into account the results of electrical resistivity of this compound the temperature dependence of the reduced Lorentz function is determined

Magnetic ordering in HoB12 below and above TN

We present results of neutron scattering experiments on frustrated antiferromagnet HoB12 above and below Ne el temperature TN. Diffuse scattering patterns indicate that above TN 7.4K pronounced correlations between neighboring magnetic moments of Ho ions appear, similar to one dimensional 1D magnets. Moreover, the diffuse scattering patterns show a symmetry reduction from fcc to simple cubic. Analogous behavior in three dimensional 3 D systems is not known, although it was predicted by theory. Results below TN and in applied magnetic field, on the other hand, reveal three amplitude modulated incommensurate magnetic structures in this compound. The role of various interactions leading to this behavior above and below TN is being discussed. Additional attention is paid also to r T resistivity dependencies in various magnetic fields close to and above the quantum critical point. PACS 72.15. v; 75.50.Ee; 78.90. t Keywords Rare earth compound; Magnetic structure; Neutron scattering; Electrical resistivit

Thermal Annealing Influence on Ions Implanted Fe-Cr Model Alloys

Binary Fe-11.62wt%Cr alloys were investigated in as-received state as well as after a two step helium ion implantation at different energies (100 keV and 250 keV) with doses up to 3.12xl018 cm-2. In order to study changes in alloys in dependence on the temperature, thermal annealing was performed at temperatures of 400, 475, 525 and 600 °C and specimens were afterwards measured by a pulsed low energy positron system (PLEPS). Annealing out of defects at lower temperatures was not as significant as expected, and we also encountered difficulties with defect identification. However, an apparent decrease of defect size was observed in the specimen annealed at a temperature of 600 °C.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen

Magnetism of rare earth tetraborides

The rare earth tetraborides REB4 with RE Ho, Er, Tm, crystallize in a tetragonal lattice where the positions of the RE ions can be mapped to a Shastry Sutherland lattice. We have investigated the magnetic properties by means of magnetisation and specific heat experiments in a magnetic field. All compounds are anisotropic, with RE Er, Tm they are strong Ising magnets, for RE Ho we find xy anisotropy. In magnetic field we find complex behaviour with a number of different phases as a function of applied field, field direction and temperature. Remarkable is the observation of fractional magnetisation plateaux for magnetic field 001 in HoB4 and TmB