Subnanosecond magnetization reversal of magnetic nanoparticle driven by chirp microwave field pulse

We investigate the magnetization reversal of single-domain magnetic nanoparticle driven by linear down-chirp microwave magnetic field pulse. Numerical simulations based on the Landau-Lifshitz-Gilbert equation reveal that solely down-chirp pulse is capable of inducing subnanosecond magnetization reversal. With a certain range of initial frequency and chirp rate, the required field amplitude is much smaller than that of constant-frequency microwave field. The fast reversal is because the down-chirp microwave field acts as an energy source and sink for the magnetic particle before and after crossing over the energy barrier, respectively. Applying a spin-polarized current additively to the system further reduces the microwave field amplitude. Our findings provide a new way to realize low-cost and fast magnetization reversal

Role of Mothers\u27 Nutritional Knowledge, Nutritional Factors on the School Performance

A cross sectional study was carried out to investigate the effects of mothers\u27 nutritional knowledge, health and nutritional factors and socio-economic parameters on school performance among class five students of University Laboratory School, Dhaka. All of the eighty students were selected for this study. This study found there is a strong relationship between mother\u27s knowledge score and school performance. It was found that mothers\u27 knowledge score was responsible for 91.1 percent change in school performance. The mean BMI of the mothers was 20.44. We found that the school performance measured by class roll number of the students is significantly related with mothers BMI. There was an imperfect negative association between socio-economic parameters and school performance. But the relationship between the school performances with socio-economic parameters was strongly significant. This study also observed the relationship between Individual Dietary Diversity Score (IDDS) of respondent and marks achieved in class 4 final exam. It is alarming that consumption percentage were low for eggs (30) and milk and milk products (37.5), but majority of the students who consumed milk and milk products (63.3%) and eggs (66.7%) got the highest marks

Magnetotransport properties of a magnetically modulated two-dimensional electron gas with the spin-orbit interaction

We study the electrical transport properties of a two-dimensional electron gas with the Rashba spin-orbit interaction in presence of a constant perpendicular magnetic field $(B_0 \hat z)$ which is weakly modulated by ${\bf B_1} = B_1 \cos (q x) \hat z$, where $B_1 \ll B_0$ and $q = 2 \pi/a$ with $a$ is the modulation period. We obtain the analytical expressions of the diffusive conductivities for spin-up and spin-down electrons. The conductivities for spin-up and spin-down electrons oscillate with different frequencies and produce beating patterns in the amplitude of the Weiss and Shubnikov-de Haas oscillations. We show that the Rashba strength can be determined by analyzing the beating pattern in the Weiss oscillation. We find a simple equation which determines the Rashba spin-orbit interaction strength if the number of Weiss oscillations between any two successive nodes is known from the experiment. We compare our results with the electrically modulated 2DEG with the Rashba interaction. For completeness, we also study the beating pattern formation in the collisional and the Hall conductivities.Comment: 11 pages, 5 figures, re-written with new result

Evolution of antiferromagnetic domains in the all-in-all-out ordered pyrochlore Nd2_2Zr2_2O7_7

We report the observation of magnetic domains in the exotic, antiferromagnetically ordered all-in-all-out state of Nd$_2$Zr$_2$O$_7$, induced by spin canting. The all-in-all-out state can be realized by Ising-like spins on a pyrochlore lattice and is established in Nd$_2$Zr$_2$O$_7$ below 0.31 K for external magnetic fields up to 0.14 T. Two different spin arrangements can fulfill this configuration which leads to the possibility of magnetic domains. The all-in-all-out domain structure can be controlled by an external magnetic field applied parallel to the [111] direction. This is a result of different spin canting mechanism for the two all-in-all-out configurations for such a direction of the magnetic field. The change of the domain structure is observed through a hysteresis in the magnetic susceptibility. No hysteresis occurs, however, in case the external magnetic field is applied along [100].Comment: Accepted for publication in Phys. Rev. B, 6 pages, 6 figure

Thermal gradient driven domain wall dynamics

The issue of whether a thermal gradient acts like a magnetic field or an electric current in the domain wall (DW) dynamics is investigated. Broadly speaking, magnetization control knobs can be classified as energy-driving or angular-momentum driving forces. DW propagation driven by a static magnetic field is the best-known example of the former in which the DW speed is proportional to the energy dissipation rate, and the current-driven DW motion is an example of the latter. Here we show that DW propagation speed driven by a thermal gradient can be fully explained as the angular momentum transfer between thermally generated spin current and DW. We found DW-plane rotation speed increases as DW width decreases. Both DW propagation speed along the wire and DW-plane rotation speed around the wire decrease with the Gilbert damping. These facts are consistent with the angular momentum transfer mechanism, but are distinct from the energy dissipation mechanism. We further show that magnonic spin-transfer torque (STT) generated by a thermal gradient has both damping-like and field-like components. By analyzing DW propagation speed and DW-plane rotation speed, the coefficient ( \b{eta}) of the field-like STT arising from the non-adiabatic process, is obtained. It is found that \b{eta} does not depend on the thermal gradient; increases with uniaxial anisotropy K_(||) (thinner DW); and decreases with the damping, in agreement with the physical picture that a larger damping or a thicker DW leads to a better alignment between the spin-current polarization and the local magnetization, or a better adiabaticity