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Using element-specific measurements of the ultrafast demagnetization of Ru/Fe$_{65}$Co$_{35}$ heterostructures, we show that Ru can exhibit a significant magnetic contrast (3% asymmetry) resulting from ultrafast spin currents emanating from the demagnetization process of the FeCo layer. We use this magnetic contrast to investigate how superdiffusive spin currents are affected by the doping of heavy elements in the FeCo layer. We find that the spin currents are strongly suppressed, and that the recovery process in Ru slows down, by Re doping. This is in accordance with a change in interface reflectivity of spin currents as found by the superdiffusive spin transport model., Comment: 7 pages, 5 figures

We present a comprehensive study of the magnetic properties of Sr$_{3-x}$Y$_{x}$(Fe$_{1.25}$Ni$_{0.75}$)O$_{7-��}$ ($0 \leq x \leq 0.75$). Experimentally, the magnetic properties are investigated using superconducting quantum interference device (SQUID) magnetometry and neutron powder diffraction (NPD). This is complemented by the theoretical study based on density functional theory as well as the Heisenberg exchange parameters. Experimental results show an increase in the N��el temperature ($T_N$) with the increase of Y concentrations and O occupancy. The NPD data reveals all samples are antiferromagnetically ordered at low temperatures, which has been confirmed by our theoretical simulations for the selected samples. Our first-principles calculations suggest that the 3D magnetic order is stabilized due to finite inter-layer exchange couplings. The latter give rise to a finite inter-layer spin correlations which disappear above the $T_N$.

Two microscopic mechanisms helping us to understand the multiferroic behavior of distorted rare-earth manganites are here briefly reviewed. The original work was carried out by means of Hamiltonian modeling and first-principles density functional simulations. Our first topic concerns the link between the Dzyaloshinskii-Moriya interaction and ferroelectricity in incommensurate magnets. We argue that the Dzyaloshinskii-Moriya interaction may play a key role since (i) it induces ferroelectric displacements of oxygen atoms and (ii) it favors the stabilization of a helical magnetic structure at low temperatures. Our second topic concerns the prediction, based on Landau theory, that the symmetry of the zigzag spin chains in the AFM-E (E-type antiferromagnetic) orthorhombic manganites (such as HoMnO3) allows a finite polarization along the c axis. The microscopic mechanism at the basis of ferroelectricity is interpreted through a gain in band energy of the e(g) electrons within the orbitally degenerate double-exchange model. Related Monte Carlo simulations have confirmed that the polarization can be much higher than what is observed in spiral magnetic phases. Density functional calculations performed on orthorhombic HoMnO3 quantitatively confirm a magnetically induced ferroelectric polarization up to similar to 6 mu C cm(-2), the largest reported so far for improper magnetic ferroelectrics. We find in HoMnO3, in addition to the conventional displacement mechanism, a sizable contribution arising from the purely electronic effect of orbital polarization. The relatively large ferroelectric polarization, present even with centrosymmetric atomic positions, is a clear sign of a magnetism-induced electronic mechanism at play, which is also confirmed by the large displacements of the Wannier function centers with respect to the corresponding ions in AFM-E HoMnO3. The final polarization is shown to be the result of competing effects, as shown by the opposite signs of the eg and t(2g) contributions to the ferroelectric polarization.

The dynamical behavior of the magnetism of diluted magnetic semiconductors (DMS) has been investigated by means of atomistic spin dynamics simulations. The conclusions drawn from the study are argued to be general for DMS systems in the low concentration limit, although all simulations are done for 5% Mn-doped GaAs with various concentrations of As antisite defects. The magnetization curve, $M(T)$, and the Curie temperature $T_C$ have been calculated, and are found to be in good correspondence to results from Monte Carlo simulations and experiments. Furthermore, equilibrium and non-equilibrium behavior of the magnetic pair correlation function have been extracted. The dynamics of DMS systems reveals a substantial short ranged magnetic order even at temperatures at or above the ordering temperature, with a non-vanishing pair correlation function extending up to several atomic shells. For the high As antisite concentrations the simulations show a short ranged anti-ferromagnetic coupling, and a weakened long ranged ferromagnetic coupling. For sufficiently large concentrations we do not observe any long ranged ferromagnetic correlation. A typical dynamical response shows that starting from a random orientation of moments, the spin-correlation develops very fast ($\sim$ 1ps) extending up to 15 atomic shells. Above $\sim$ 10 ps in the simulations, the pair correlation is observed to extend over some 40 atomic shells. The autocorrelation function has been calculated and compared with ferromagnets like bcc Fe and spin-glass materials. We find no evidence in our simulations for a spin-glass behaviour, for any concentration of As antisites. Instead the magnetic response is better described as slow dynamics, at least when compared to that of a regular ferromagnet like bcc Fe., Comment: 24 pages, 15 figures

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The experience in treating three patients with hemangiopericytoma is reviewed. One patient was given irradiation alone, and the others were both treated with surgery and irradiation. Our experience reinforces reports of the usefulness of irradiation in treating this neoplasm and its metastases.

Out of 840 cases of breast carcinoma seen over a period of ten years, 18 were found to be associated with pregnancy and lactation. According to the mode of onset and presentation of the disease, these patients were divided into four groups. The average age of these patients was 31.9 years old. Thirteen out of 18 patients presented in a very advanced stage of the disease. In a short period, involvement of liver was noticed in 8, brain in 3, and bones and lung in 2 each. The disease was bilaterally simultaneous in two patients. The acceleration of growth was noticed during second and third trimesters of pregnancy as well as during lactation. The termination of pregnancy in three patients did not alter the clinical course of the disease.Of 840 cases of breast cancer seen at a clinic in India over a 10-year period, 18 (2.1%) were discovered concomitant with pregnancy and lactation. Records from the study are tabulated. 4 women experienced onset and presentation of the disease during lactation, 4 others experienced onset during pregnancy and presentation during lactation, 6 had an onset of the disease before pregnancy and presentation during pregnancy, 3 had onset of the disease before pregnancy and presentation during lactation, and 1 had a pregnancy subsequent to the occurrence of the disease. The average age of the patients was 31.9 years old. Duration of the presenting symptoms was short and progression of the disease was rapid. Of the 20 affected breasts, all quadrants were involved in 11, indicating the aggressive nature of the disease. Treatment ranged from lumpectomy to radical mastectomy, palliative to radical radiotherapy, ablative or additive hormone therapy, and termination of pregnancy. The prognosis for breast cancer discovered during pregnancy and lactation is poor with the tumor growing and metastasizing rapidly. Some of the relevant literature indicates that increased vascular and lymphatic supply may provide a favorable medium for the growth and metastatic spread. The end of the 2nd and 3rd trimesters of pregnancy and lactation was particularly responsible for accelerated growth of the tumor. The effects of hormones associated with pregnancy and lactation are unclear. Interruption of the pregnancy does not seem to improve survival times.

Extramedullary plasmacytoma occurs infrequently as compared to osseous myoloma. A single case of extramedullary plasmacytoma was seen during the last 10 years whose initial presentation was that of a soft tissue sarcoma of the chest wall. Clinical data along with relevent investigation and treatment results are discussed with a review of the literature.

Recent experimental investigations show that large area samples of graphene tend to be polycrystalline. Physical properties of such samples are strongly affected by the presence of intrinsic topological defects of polycrystalline materials—dislocations and grain boundaries. This article reviews recent progress in understanding dislocations and grain boundaries in graphene. First a systematic approach towards constructing topological defects in graphene is introduced. Then the review discusses the formation energies of these defects stressing the dramatic stabilization of dislocations and small angle grain boundaries in graphene due to the two dimensional nature of this material. Finally the electronic transport properties of polycrystalline graphene are considered showing that topological defects may present novel opportunities towards engineering electronic devices based on graphene.