In this work we report the appearence of a large perpendicular magnetic anisotropy (PMA) in Fe1−xGax thin films grown onto ZnSe/GaAs(100). This arising anisotropy is related to the tetragonal ...metastable phase in as-grown samples recently reported M. Eddrief {\it et al.}, Phys. Rev. B {\bf 84}, 161410 (2011). By means of ferromagnetic resonance studies we measured PMA values up to ∼ 5×105 J/m3. PMA vanishes when the cubic structure is recovered upon annealing at 300∘C. Despite the important values of the magnetoelastic constants measured via the cantilever method, the consequent magnetoelastic contribution to PMA is not enough to explain the observed anisotropy values in the distorted state. {\it Ab initio} calculations show that the chemical ordering plays a crucial role in the appearance of PMA. Through a phenomenological model we are able to explain that an excess of next nearest neighbour Ga pairs (B2-like ordering) along the perpendicular direction arises as the source of PMA in Fe1−xGax thin films.
•The phase and orientation are independent of the Mn effusion cell temperature.•The layer is evenly covered with Mn and the TEM shows no other Mn-rich structure.•MCE shows a high ΔSm spread in a ...wider temperature range, relative to bulk Mn5Ge3.
Mn5Ge3 thin films were grown on GaAs(111) and GaAs(001) by Molecular Beam Epitaxy (MBE). The influence of stoichiometry and alloying of the samples was investigated using different Mn diffusion cell temperatures for each sample. X-ray diffraction (XRD) measurements reveal the following epitaxial relations: (001) Mn5Ge3//(111) GaAs and 110 Mn5Ge3//2–1–1 GaAs for the sample grown on GaAs(111), and (111) Mn5Ge3//(001) GaAs and −110 Mn5Ge3//110 GaAs for the samples grown on GaAs(001). High-resolution transmission electron microscopy (HRTEM) results for a sample grown on GaAs(001) indicate that samples are around 70 nm thick and are composed of several grains with 2 different orientations corresponding to a 90° rotation around the 111 axis. Analyzing the Mn map with energy-filtered transmission electron microscopy (EFTEM) we observed that all the grains look very similar, indicating that they contain roughly the same amount of manganese. The magnetocaloric effect found in both family of samples is spread in a wider temperature range when compared with bulk Mn5.1Ge2.9 and the magnetic entropy change peak is higher than Si- or Sb- modified Mn5Ge3. This result makes the Mn5Ge3 a possible candidate for magnetic refrigeration while being a rare earth-free material.
To evaluate whether two commonly used newer platinum-based regimens offer any advantage over vinorelbine-cisplatin (reference regimen) in response rate for patients with advanced non-small-cell lung ...cancer (NSCLC).
Chemotherapy-naive patients were randomized to receive gemcitabine 1,250 mg/m(2) days 1 and 8 plus cisplatin 75 mg/m(2) day 2 every 21 days (GC arm), or paclitaxel 225 mg/m(2) (3-hour infusion) then carboplatin (area under the concentration-time curve of 6 mg/mL x min), both on day 1 every 21 days (PCb arm), or vinorelbine 25 mg/m(2)/wk for 12 weeks then every other week plus cisplatin 100 mg/m(2) day 1 every 28 days (VC arm).
Six hundred twelve patients were randomized to treatment (205 GC, 204 PCb, and 203 VC). Overall response rates for the GC (30%) and PCb (32%) arms were not significantly different from that of the VC arm (30%). There were no differences in overall survival, time to disease progression, or time to treatment failure. Median survival for the GC, PCb, and VC groups was 9.8, 9.9, and 9.5 months, respectively. Neutropenia was significantly higher on the VC arm (GC 17% or PCb 35% v VC 43% of cycles, P <.001), as was thrombocytopenia on the GC arm (GC 16% v VC 0.1% of cycles, P <.001). Alopecia and peripheral neurotoxicity were most common on the PCb arm, as was nausea/vomiting on the VC arm (P <.05).
Efficacy end points were not significantly different between experimental and reference arms, although toxicities showed differences. These findings suggest that chemotherapy in NSCLC has reached a therapeutic plateau.
Magnetotransport properties of Fe0.8Ga0.2 films with stripe domains are studied. The anisotropic magnetoresistance dominates the low field behavior, which is extremely dependent on the magnetic ...domains configuration. The magnetoresistance measured at different temperatures displays qualitatively different behaviors depending on the measurement configuration. When the stripes are oriented along the electric current, the low-field magnetoresistance changes sign with temperature, while when the stripes are perpendicular to the electric current the magnetoresistance curves are nearly temperature independent. A simple model considering parallel (series) conduction along (across) the stripes, plus the temperature dependence of anisotropic magnetoresistance and domains configuration, accounts for these experimental results.
In this work we report the appearance of a large perpendicular magnetic anisotropy (PMA) in Fe1−xGax thin films grown onto ZnSe/GaAs(001). This arising anisotropy is related to the tetragonal ...metastable phase in as-grown samples recently reported M. Eddrief et al., Phys. Rev. B 84, 161410 (2011). By means of ferromagnetic resonance studies we measured PMA values up to ∼5×105 J/m3. PMA vanishes when the cubic structure is recovered upon annealing at 300∘C. Despite the important values of the magnetoelastic constants measured via the cantilever method, the consequent magnetoelastic contribution to PMA is not enough to explain the observed anisotropy values in the distorted state. Ab initio calculations show that the chemical ordering plays a crucial role in the appearance of PMA. Through a phenomenological model we propose that an excess of next-nearest-neighbor Ga pairs (B2-like ordering) along the perpendicular direction arises as a possible source of PMA in Fe1−xGax thin films.
In thin magnetic films with perpendicular magnetic anisotropy, a periodic "up-down" stripe-domain structure can be originated at remanence, on a mesoscopic scale (~100 nm) comparable with film ...thickness, by the competition between short-range exchange coupling and long-range dipolar interaction. However, translational order is perturbed because magnetic edge dislocations are spontaneously nucleated. Such topological defects play an important role in magnetic films since they promote the in-plane magnetization reversal of stripes and, in superconductor/ferromagnet hybrids, the creation of superconducting vortex clusters. Combining magnetic force microscopy experiments and micromagnetic simulations, we investigated the motion of two classes of magnetic edge dislocations, randomly distributed in an Formula: see text-implanted Fe film. They were found to move in opposite directions along straight trajectories parallel to the stripes axis, when driven by a moderate dc magnetic field. Using the approximate Thiele equation, analytical expressions for the forces acting on such magnetic defects and a microscopic explanation for the direction of their motion could be obtained. Straight trajectories are related to the presence of a periodic stripe domain pattern, which imposes the gyrotropic force to vanish even if a nonzero, half-integer topological charge is carried by the defects in some layers across the film thickness.
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