A. Liebig

Photoluminescence emission and Raman response of monolayer MoS 2 , MoSe 2 , and WSe 2

We mechanically exfoliate mono- and few-layers of the transition metal dichalcogenides molybdenum disulfide, molybdenum diselenide, and tungsten diselenide. The exact number of layers is unambiguously determined by atomic force microscopy and high-resolution Raman spectroscopy. Strong photoluminescence emission is caused by the transition from an indirect band gap semiconductor of bulk material to a direct band gap semiconductor in atomically thin form.

Thermally Assisted All‐Optical Helicity Dependent Magnetic Switching in Amorphous Fe100–xTbx Alloy Films

All-optical switching (AOS) in ferrimagnetic Fe(100-x)Tb(x) alloys is presented. AOS is witnessed below, above, and in samples without a magnetic compensation point. It is found that AOS is associated with laser heating up to the Curie temperature and intimately linked to a low remanent sample magnetization. Above a threshold magnetization of 220 emu/cc helicity dependent AOS is replaced by pure thermal demagnetization.

Colossal thermoelectric power in Gd-Sr manganites

Manganites belonging to the series Gd1−xSrxMnO3 (x=0.3, 0.4 and 0.5) were prepared by wet solid-state reaction and their thermoelectric power was evaluated. Thermoelectric power measurements revealed a peak value at ~40u2009K. All the samples exhibited a colossal thermopower at ~40u2009K and in that Gd0.5Sr0.5MnO3 exhibited a maximum value of ~35u2009mV/K, which is the largest reported for these class of materials at this temperature. Temperature-dependent magnetisation measurements showed that the samples exhibit a phase transition from paramagnetic to spin-glass–like state at these temperatures. Plausible mechanisms responsible for the observed colossal thermoelectric power in Gd-Sr manganites are discussed.

Magnetization Reversal in Arrays of Magnetic Nanoperforations

Nanoperforated ZrO2 membranes, produced via organic/inorganic self-assembly using block copolymer micelles, serve as template for a Co/Pt multilayer stack with out-of-plane magnetic anisotropy. The deposition of the magnetic film results in an array of magnetic nanodots surrounded by a continuous magnetic film. These magnetic dots are found to be in a single-domain state and appear as magnetically exchange isolated from the surrounding film. The latter observation can be related to the specific morphology of the nanoperforations. In addition, strong domain-wall pinning of the continuous magnetic film at the locations of the nanoperforations was observed. Therefore, this approach is promising to create a percolated magnetic medium, which is considered as future recording media.

Exchange bias effect in partially oxidized amorphous Fe–Ni–B based metallic glass nanostructures

The magnetic properties of amorphous Fe-Ni-B based metallic glass nanostructures were investigated. The nanostructures underwent a spin-glass transition at temperatures below 100 K and revealed an irreversible temperature following the linear de Almeida-Thouless dependence. When the nanostructures were cooled below 25 K in a magnetic field, they exhibited an exchange bias effect with enhanced coercivity. The observed onset of exchange bias is associated with the coexistence of the spin-glass phase along with the appearance of another spin-glass phase formed by oxidation of the structurally disordered surface layer, displaying a distinct training effect and cooling field dependence. The latter showed a maximum in exchange bias field and coercivity, which is probably due to competing multiple equivalent spin configurations at the boundary between the two spin-glass phases.

Chemical ordering of FePt films using millisecond flash-lamp annealing

The structural and magnetic properties of 20-nm-thick FexPt100-x films that were processed by 20u2009ms flash-lamp annealing were investigated. A maximum in coercivity of (10.4u2009±u20090.5) kOe was achieved for a composition of Fe53Pt47, which shows also a high degree of L10 chemical order. A variation of the chemical composition toward either higher or lower Fe content leads to a lowering of the coercivity, which can be attributed to a reduction in L10 ordered volume fraction. Thus, in the millisecond time regime, the fastest ordering transformation occurs for slightly Fe-rich FePt films.

Thermally Assisted All-Optical Helicity Dependent Switching of Ferrimagnetic Amorphous Fe 100− x Tb x Thin Films

We observe all-optical switching (AOS) in ferrimagnetic Fe100−x Tb x alloy films below, above, and in samples without a magnetic compensation point. AOS is linked to a low remanent magnetization M R and associated with laser heating up to the Curie temperature. Above M R = 220 emu/cc AOS is replaced by pure thermal demagnetization.