scholarly journals Micromagnetic simulation of THz signals in antiferromagnetic FeRh by sub-picosecond thermal pulses

AIP Advances ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 035040 ◽  
Author(s):  
Marco Menarini ◽  
Rajasekhar Medapalli ◽  
Eric E. Fullerton ◽  
Vitaliy Lomakin
Keyword(s):  
Micromagnetic Simulation ◽  
Thermal Pulses

scholarly journals Carbon star wind models at solar and sub-solar metallicities: a comparative study

2019 ◽  
Vol 623 ◽  
pp. A119 ◽  
Author(s):  
S. Bladh ◽  
K. Eriksson ◽  
P. Marigo ◽  
S. Liljegren ◽  
B. Aringer
Keyword(s):  
Mass Loss ◽  
Agb Stars ◽  
Carbon Stars ◽  
Dust Production ◽  
Grain Sizes ◽  
Solar Metallicity ◽  
Effective Temperatures ◽  
Carbon Excess ◽  
Thermal Pulses ◽  
Loss Rates

Context. The heavy mass loss observed in evolved stars on the asymptotic giant branch (AGB) is usually attributed to dust-driven winds, but it is still an open question how much AGB stars contribute to the dust production in the interstellar medium, especially at lower metallicities. In the case of C-type AGB stars, where the wind is thought to be driven by radiation pressure on amorphous carbon grains, there should be significant dust production even in metal-poor environments. Carbon stars can manufacture the building blocks needed to form the wind-driving dust species themselves, irrespective of the chemical composition they have, by dredging up carbon from the stellar interior during thermal pulses. Aims. We investigate how the mass loss in carbon stars is affected by a low-metallicity environment, similar to the Large and Small Magellanic Clouds (LMC and SMC). Methods. The atmospheres and winds of C-type AGB stars are modeled with the 1D spherically symmetric radiation-hydrodynamical code Dynamic Atmosphere and Radiation-driven Wind models based on Implicit Numerics (DARWIN). The models include a time-dependent description for nucleation, growth, and evaporation of amorphous carbon grains directly out of the gas phase. To explore the metallicity-dependence of mass loss we calculate model grids at three different chemical abundances (solar, LMC, and SMC). Since carbon may be dredged up during the thermal pulses as AGB stars evolve, we keep the carbon abundance as a free parameter. The models in these three different grids all have a current mass of one solar mass; effective temperatures of 2600, 2800, 3000, or 3200 K; and stellar luminosities equal to logL*∕L⊙ = 3.70, 3.85, or 4.00. Results. The DARWIN models show that mass loss in carbon stars is facilitated by high luminosities, low effective temperatures, and a high carbon excess (C–O) at both solar and subsolar metallicities. Similar combinations of effective temperature, luminosity, and carbon excess produce outflows at both solar and subsolar metallicities. There are no large systematic differences in the mass-loss rates and wind velocities produced by these wind models with respect to metallicity, nor any systematic difference concerning the distribution of grain sizes or how much carbon is condensed into dust. DARWIN models at subsolar metallicity have approximately 15% lower mass-loss rates compared to DARWIN models at solar metallicity with the same stellar parameters and carbon excess. For both solar and subsolar environments typical grain sizes range between 0.1 and 0.5 μm, the degree of condensed carbon varies between 5 and 40%, and the gas-to-dust ratios between 500 and 10 000. Conclusions. C-type AGB stars can contribute to the dust production at subsolar metallicities (down to at least [Fe∕H] = −1) as long as they dredge up sufficient amounts of carbon from the stellar interior. Furthermore, stellar evolution models can use the mass-loss rates calculated from DARWIN models at solar metallicity when modeling the AGB phase at subsolar metallicities if carbon excess is used as the critical abundance parameter instead of the C/O ratio.

scholarly journals Micromagnetic simulation of exchange coupled ferri-/ferromagnetic heterostructures

2015 ◽  
Vol 381 ◽  
pp. 28-33 ◽  
Author(s):  
Harald Oezelt ◽  
Alexander Kovacs ◽  
Franz Reichel ◽  
Johann Fischbacher ◽  
Simon Bance ◽  
...  
Keyword(s):  
Micromagnetic Simulation

Micromagnetic simulation of the coercivity mechanism in Sm(Co,Fe,Cu,Zr)z magnets

2004 ◽  
Vol 95 (3) ◽  
pp. 1351-1356 ◽  
Author(s):  
Chuan-bing Rong ◽  
Hong-wei Zhang ◽  
Jian Zhang ◽  
Xiao-bo Du ◽  
Shao-ying Zhang ◽  
...  
Keyword(s):  
Micromagnetic Simulation ◽  
Coercivity Mechanism

scholarly journals Spin-wave duplexer studied by finite-element micromagnetic simulation

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Sang-Koog Kim ◽  
Hyeon-Kyu Park ◽  
Jaehak Yang ◽  
Junhoe Kim ◽  
Myoung-Woo Yoo
Keyword(s):  
Finite Element ◽  
Spin Wave ◽  
Micromagnetic Simulation

Micromagnetic Simulation of Propagation of Spin Waves in In-Plane Magnetized Crosses Based on Ferrite Microwaveguides of Different Width

2018 ◽  
Vol 63 (10) ◽  
pp. 1212-1216 ◽  
Author(s):  
G. M. Dudko ◽  
A. V. Kozhevnikov ◽  
Yu. V. Khivintsev ◽  
Yu. A. Filimonov ◽  
A. G. Khitun ◽  
...  
Keyword(s):  
Spin Waves ◽  
Micromagnetic Simulation
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