Magnetic Aging

2005 ◽  
Vol 887 ◽  
Author(s):  
R. Skomski ◽  
J. Zhou ◽  
R. D. Kirby ◽  
D. J. Sellmyer
Keyword(s):  
Free Energy ◽  
Power Law ◽  
Magnetization Reversal ◽  
Eddy Currents ◽  
Scientific Research ◽  
Magnetization Dynamics ◽  
Energy Barriers ◽  
Thermally Activated ◽  
Magnetic Aging ◽  
Magnetization Processes

ABSTRACTThermally activated magnetization reversal is of great importance in areas such as permanent magnetism and magnetic recording. In spite of many decades of scientific research, the phenomenon of slow magnetization dynamics has remained partially controversial. It is now well-established that the main mechanism is thermally activated magnetization reversal, as contrasted to eddy currents and structural aging, but the identification of the involved energy barriers remains a challenge for many systems. Thermally activated slow magnetization processes proceed over energy barriers whose structure is determined by the micromagnetic free energy. This restricts the range of physically meaningful energy barriers. An analysis of the underlying micromagnetic free energy yields power-law dependences with exponents of 3/2 or 2 for physically reasonable models, in contrast to arbitrary exponents m and to 1/H-type laws.

Determination of eddy current losses and hysteresis losses in magnetic circuits of electrical machines

2020 ◽  
pp. 54-58
Author(s):  
S. M. Plotnikov
Keyword(s):  
Eddy Current ◽  
Magnetization Reversal ◽  
Eddy Currents ◽  
Technical Problem ◽  
Electrical Machines ◽  
Eddy Current Losses ◽  
Hysteresis Losses ◽  
Magnetic Circuits ◽  
Core Losses ◽  
Reversal Frequency

The division of the total core losses in the electrical steel of the magnetic circuit into two components – losses dueto hysteresis and eddy currents – is a serious technical problem, the solution of which will effectively design and construct electrical machines with magnetic circuits having low magnetic losses. In this regard, an important parameter is the exponent α, with which the frequency of magnetization reversal is included in the total losses in steel. Theoretically, this indicator can take values from 1 to 2. Most authors take α equal to 1.3, which corresponds to the special case when the eddy current losses are three times higher than the hysteresis losses. In fact, for modern electrical steels, the opposite is true. To refine the index α, an attempt was made to separate the total core losses on the basis that the hysteresis component is proportional to the first degree of the magnetization reversal frequency, and the eddy current component is proportional to the second degree. In the article, the calculation formulas of these components are obtained, containing the values of the total losses measured in idling experiments at two different frequencies, and the ratio of these frequencies. It is shown that the rational frequency ratio is within 1.2. Presented the graphs and expressions to determine the exponent α depending on the measured no-load losses and the frequency of magnetization reversal.

Calculation of the free energy barriers in the oligomerisation of Ab

10.2741/3104 ◽  
2008 ◽  
Vol Volume (13) ◽  
pp. 5614 ◽  
Author(s):  
Mookyung Cheon
Keyword(s):  
Free Energy ◽  
Energy Barriers

Asymmetric magnetic disorder observed in thermally activated magnetization reversal of exchange-biased IrMn/CoFe films

2013 ◽  
Vol 325 ◽  
pp. 13-16 ◽  
Author(s):  
Hun-Sung Lee ◽  
Kwang-Su Ryu ◽  
Chun-Yeol You ◽  
Kun-Rok Jeon ◽  
See-Hun Yang ◽  
...  
Keyword(s):  
Magnetization Reversal ◽  
Thermally Activated ◽  
Magnetic Disorder

Microscopic mechanisms of initial oxidation of Si(100): Reaction pathways and free-energy barriers

2012 ◽  
Vol 85 (20) ◽  
Author(s):  
Kenichi Koizumi ◽  
Mauro Boero ◽  
Yasuteru Shigeta ◽  
Atsushi Oshiyama
Keyword(s):  
Free Energy ◽  
Reaction Pathways ◽  
Energy Barriers ◽  
Initial Oxidation

Power Law Size-Distributed Heterogeneity Explains Colloid Retention on Soda Lime Glass in the Presence of Energy Barriers

Langmuir ◽  
2014 ◽  
Vol 30 (19) ◽  
pp. 5412-5421 ◽  
Author(s):  
Eddy Pazmino ◽  
Jacob Trauscht ◽  
Brittany Dame ◽  
William P. Johnson
Keyword(s):  
Power Law ◽  
Soda Lime ◽  
Soda Lime Glass ◽  
Energy Barriers ◽  
Colloid Retention

Nucleation free-energy barriers with Hybrid Monte-Carlo/Umbrella Sampling

2014 ◽  
Vol 16 (45) ◽  
pp. 24913-24919 ◽  
Author(s):  
M. A. Gonzalez ◽  
E. Sanz ◽  
C. McBride ◽  
J. L. F. Abascal ◽  
C. Vega ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Free Energy ◽  
Umbrella Sampling ◽  
Energy Barriers ◽  
Hybrid Monte Carlo

Diffusion-Induced Grain Boundary Migration and Role of Defects

1993 ◽  
Vol 319 ◽  
Author(s):  
T.K. Chaki
Keyword(s):  
Free Energy ◽  
Grain Boundary ◽  
Boundary Migration ◽  
Solute Concentration ◽  
Grain Boundary Migration ◽  
Thermally Activated ◽  
Energy Of Mixing ◽  
Free Energy Of Mixing ◽  
Liquid Film Migration ◽  
Lattice Diffusivity

AbstractA model is presented to explain various aspects of diffusion-induced grain boundary migration (DIGM). The driving energies of DIGM are identified as the free energy of mixing and the interface free energy, the former being predominant in most cases of DIGM. The grain boundary migrates due to thermally activated motion of atoms across the interface under the influence of the driving energies. An expression for the velocity of migration is derived. It is shown that this depends parabolically on the solute concentration, in agreement with experimental observations in the case of liquid film migration (LFM), which is analogous to DIGM. Furthermore, the velocity is proportional to lattice diffusivity ahead of the boundary. Recent results of enhancement of DIGM by ion bombardment is explained by radiation-enhanced lattice diffusivity due to introduction of point defects by the ions. The model also explains that diffusion-induced recrystallization (DIR) is due to a free energy decrease associated with the transformation from the amorphous phase in the grain boundary layer to the crystalline phase.

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