Results 1 - 10 of 10315
Results 1 - 10 of 10315. Search took: 0.03 seconds
|Sort by: date | relevance|
[en] Type II multiferroics are magnetically ordered phases that exhibit ferroelectricity as a magnetic induced effect. We show that in single-k magnetic phases the presence in the paramagnetic phase of non-symmorphic symmetry combined with some specific type of magnetic propagation vector can be sufficient for the occurrence of this type of multiferroic behaviour. Other symmetry scenarios especially favourable for spin driven multiferroicity are also presented. We review and classify known type II multiferroics under this viewpoint. In addition, some other magnetic phases which due to their symmetry properties can exhibit type II multiferroicity are pointed out. (paper)
[en] Complete text of publication follows. The Anisotropy of Magnetic Susceptibility (AMS) at room temperature has been used for decades as a means to gain further understanding of petrofabrics within granites. Hence, the orientation of the magnetic ellipsoid is used as a kinematic marker for the emplacement mechanism of granitic bodies. In order to secure a correct interpretation of AMS as a result of magmatic fabric, one factor must be considered: the carrier of the AMS. In the case of the paramagnetic Marimanha igneous body, the carrier of the magnetic fabric is biotite (Antolin et al., 2007), which represents 20-25 % vol. as seen in thin section. Five sites chosen from the five petrographic zonations of the plutonic body are further studied via image analyses of biotites and crystallographic preferred orientations (CPOs) of quartz. On one hand there will be an external control of the AMS with the image analyses of biotite and on the other, more information of the orientation of quartz grains provide new data about the behavior of crystals during emplacement. In addition, the relationship between paramagnetic and diamagnetic grains will be established. The image analyses followed two approaches, on one side, the orientation of the biotite is studied in three perpendicular thin sections and on the other, the basal planes of biotites are represented as lines, whose orientation is subsequently studied again in the same thin sections. The crystallographic orientations of quartz c-axes were measured using electron backscatter diffraction (EBSD) analyses. In addition, cooled samples (down to 77degK) are analyzed to obtain the LT-AMS and to compare with the AMS at room temperature. Preliminary results from this weakly oriented granitoid suggest that the paramagnetic mineral biotite is the carrier of the AMS at room and at low temperature. Image analyses seem to have different solutions for every site and do not correspond directly to AMS results. The orientation of quartz c-axes is different in the five sites. These results are discussed in terms of crystal orientation, rock composition and influence of the shape and degree of anisotropy of the orientation ellipsoid.
[en] The paramagnetic Meissner effect (PME) was investigated in Nb samples which showed the PME already 20 years ago 1. Magnetization measurements (M(T) and M(H))were performed using different magnetometers (QD SQUID MPMS3 and PPMS). We could reproduce the same PME behavior of the samples, despite the long storage time. In this contribution, we compare the old results from 1997 to the new data. The M(T)-data reveal the same principal features at the superconducting transition, and the M(H)-data measured close to the superconducting transition exhibit a change of the shape of the magnetization loops as in the original experiments. Furthermore, we also observe the features of the PME transition to much higher fields as reported previously. The measurements proof that the sample surfaces were not altered due to storage.
[en] Magnetization of finite size systems in the form of mesoscopic rings has intrigued physicists for a long time. Theories to date predict paramagnetic behavior, but experiments consistently show diamagnetic behavior. We show that the evanescent modes that are always present in rings of finite thicknesses can carry very large diamagnetic currents that are also very sensitive to disorder. Their contribution has always been ignored so far. Their contribution has features similar to that observed in experiments
[en] The first spectroscopic evidence for dia- and paramagnetic domains (Condon domains) in beryllium metal is presented. The domains, detected by the splitting of the μSR line, arise and disappear periodically in each de Haas-van Alphen cycle as the field H, normal to the single crystal Be plate and parallel to its  axis, is tuned near H0 ∼ 2.7 T. The intensity of the lines in the doublet reflect the ratio of dia- to paramagnetic regions. For the difference in induction within the domains we obtain Δ B ∼ 30-40 G in the investigated field range at T=0.8 K
[en] This paper briefly reviews the advances made in recent years at the E K Zavoisky Kazan Physical-Technical Institute of the Russian Academy of Sciences in EPR spectroscopy and its applications to overcoming the topical problems (conferences and symposia. 70th anniversary of the e k zavoisky kazan physical-technical institute, kazan scientific center of the russian academy of sciences)
[en] The electrical conduction in both metallic and semiconducting phase of La1−xKxMnO3 (x = 0.05, 0.1, 0.15) is investigated. The phonon frequencies are estimated from the ab initio theory with calibrated Hamiltonian for the atomic interaction between a pair such as Mn–O and La/K–O including van der Walls interaction. The classical electron–phonon model of resistivity, i.e., the Bloch–Gruneisen (BG) model consistently retraces the reported metallic resistivity behavior. The paramagnetic semiconducting nature is discussed with thermal activation, small polaron conduction and Mott’s variable range hopping model. The comparison of experimental data appears favorable with the present analysis