687 research outputs found
Activation of additional energy dissipation processes in the magnetization dynamics of epitaxial chromium dioxide films
The precessional magnetization dynamics of a chromium dioxide film is
examined in an all-optical pump-probe setup. The frequency dependence on the
external field is used to extract the uniaxial in-plane anisotropy constant.
The damping shows a strong dependence on the frequency, but also on the laser
pump fluency, which is revealed as an important experiment parameter in this
work: above a certain threshold further channels of energy dissipation open and
the damping increases discontinuously. This behavior might stem from spin-wave
instabilities
Analytical expression of the magneto-optical Kerr effect and Brillouin light scattering intensity arising from dynamic magnetization
Time-resolved magneto-optical Kerr effect (MOKE) and Brillouin light
scattering (BLS) spectroscopy are important techniques for the investigation of
magnetization dynamics. Within this article, we calculate analytically the MOKE
and BLS signals from prototypical spin-wave modes in the ferromagnetic layer.
The reliability of the analytical expressions is confirmed by optically exact
numerical calculations. Finally, we discuss the dependence of the MOKE and BLS
signals on the ferromagnetic layer thickness
Comparison of the magneto-Peltier and magneto-Seebeck effects in magnetic tunnel junctions
Understanding heat generation and transport processes in a magnetic tunnel
junction (MTJ) is a significant step towards improving its application in
current memory devices. Recent work has experimentally demonstrated the
magneto-Seebeck effect in MTJs, where the Seebeck coefficient of the junction
varies as the magnetic configuration changes from a parallel (P) to an
anti-parallel (AP) configuration. Here we report the study on its
as-yet-unexplored reciprocal effect, the magneto-Peltier effect, where the heat
flow carried by the tunneling electrons is altered by changing the magnetic
configuration of the MTJ. The magneto-Peltier signal that reflects the change
in the temperature difference across the junction between the P and AP
configurations scales linearly with the applied current in the small bias but
is greatly enhanced in the large bias regime, due to higher-order Joule heating
mechanisms. By carefully extracting the linear response which reflects the
magneto-Peltier effect, and comparing it with the magneto-Seebeck measurements
performed on the same device, we observe results consistent with Onsager
reciprocity. We estimate a magneto-Peltier coefficient of 13.4 mV in the linear
regime using a three-dimensional thermoelectric model. Our result opens up the
possibility of programmable thermoelectric devices based on the Peltier effect
in MTJs
Nanofabrication of spin-transfer torque devices by a PMMA mask one step process: GMR versus single layer devices
We present a method to prepare magnetic spin torque devices of low specific
resistance in a one step lithography process. The quality of the pillar devices
is demonstrated for a standard magnetic double layer device. For single layer
devices, we found hysteretic switching and a more complex dynamical excitation
pattern in higher fields. A simple model to explain the resistance spikes is
presented.Comment: 22 pages, 6 figures, submitted to J. Appl. Phy
Alpha-decay properties of superheavy elements in the relativistic mean-field theory with vector self-coupling of meson
We have investigated properties of -decay chains of recently produced
superheavy elements Z=115 and Z=113 using the new Lagrangian model NL-SV1 with
inclusion of the vector self-coupling of meson in the framework of the
relativistic mean-field theory. It is shown that the experimentally observed
alpha-decay energies and half-lives are reproduced well by this Lagrangian
model. Further calculations for the heavier elements with Z=117-125 show that
these nuclei are superdeformed with a prolate shape in the ground state. A
superdeformed shell-closure at Z=118 lends an additional binding and an extra
stability to nuclei in this region. Consequently, it is predicted that the
corresponding values provide -decay half-lives for heavier
superheavy nuclei within the experimentally feasible conditions. The results
are compared with those of macroscopic-microscopic approaches. A perspective of
the difference in shell effects amongst various approaches is presented and its
consequences on superheavy nuclei are discussed.Comment: Revised version, 14 pages, 12 eps figures. To appear in PRC.
Discussion on shell effects is shortened in the revised version. However,
commonality of the role of shell effects in extreme superheavy regions and in
the regions near the r-process path is maintained. Existence of a secondary
superdeformed minimum for Z=113 is verified with another Lagrangian se
- …