3,365 research outputs found
Room temperature soft ferromagnetism in the nanocrystalline form of YCo2 - a well-known bulk Pauli paramagnet
The Laves phase compound, YCo2, is a well-known exchange-enahnced Pauli
paramagnet. We report here that, in the nanocrystalline form, this compound
interestingly is an itinerant ferromagnet at room temperature with a low
coercive-field. The magnitude of the saturation moment (about 1 Bohr-magneton
per formula unit) is large enough to infer that the ferromagnetism is not a
surface phenomenon in these nanocrystallites. Since these ferromagnetic
nanocrystallines are easy to synthesize with a stable form in air, one can
explore applications, particularly where hysteresis is a disadvantage
Predictive control of wind turbines by considering wind speed forecasting techniques
A wind turbine system is operated such that the points of wind rotor curve and electrical generator curve coincide. In order to obtain maximum power output of a wind turbine generator system, it is necessary to drive the wind turbine at an optimal rotor speed for a particular wind speed. A Maximum Power Point Tracking (MPPT) controller is used for this purpose. In fixed-pitch variable-speed wind turbines, wind-rotor parameters are fixed and the restoring torque of the generator needs to be adjusted to maintain optimum rotor speed at a particular wind speed for optimum power output. In turbulent wind environment, control of variable-speed fixed-pitch wind turbine systems to continuously operate at the maximum power points becomes difficult due to fluctuation of wind speeds. In this paper, wind speed forecasting techniques will be considered for predictive optimum control system of wind turbines
Magnetocaloric effect and nature of magnetic transition in nanoscale Pr0.5Ca0.5MnO3
Systematic measurements pertinent to the magnetocaloric effect and nature of
magnetic transition around the transition temperature are performed in the 10
nm Pr0.5Ca0.5MnO3 nanoparticles (PCMO10) . Maxwell relation is employed to
estimate the change in magnetic entropy. At Curie temperature TC, 83.5 K, the
change in magnetic entropy discloses a typical variation with a value 0.57 J/kg
K, and is found to be magnetic field dependent. From the area under the curve
Delta S vs T, the refrigeration capacity is calculated at TC, 83.5 K and it is
found to be 7.01 J/kg. Arrott plots infer that due to the competition between
the ferromagnetic and anti ferromagnetic interactions, the magnetic phase
transition in PCMO10 is broadly spread over both in temperature as well as in
magnetic field coordinates. Upon tuning the particle size, size distribution,
morphology, and relative fraction of magnetic phases, it may be possible to
enhance the magnetocalorific effect further in PCMO10.Comment: Accepted (Journal of Applied Physics) (In press
Resistive switching in ultra-thin La0.7Sr0.3MnO3 / SrRuO3 superlattices
Superlattices may play an important role in next generation electronic and
spintronic devices if the key-challenge of the reading and writing data can be
solved. This challenge emerges from the coupling of low dimensional individual
layers with macroscopic world. Here we report the study of the resistive
switching characteristics of a of hybrid structure made out of a superlattice
with ultrathin layers of two ferromagnetic metallic oxides, La0.7Sr0.3MnO3
(LSMO) and SrRuO3 (SRO). Bipolar resistive switching memory effects are
measured on these LSMO/SRO superlattices, and the observed switching is
explainable by ohmic and space charge-limited conduction laws. It is evident
from the endurance characteristics that the on/off memory window of the cell is
greater than 14, which indicates that this cell can reliably distinguish the
stored information between high and low resistance states. The findings may
pave a way to the construction of devices based on nonvolatile resistive memory
effects
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