scholarly journals ON THE TRANSITION BETWEEN FERROMAGNETIC AND PARAMAGNETIC STATES IN MESOPOROUS MATERIALS WITH FRACTAL MORPHOLOGY

2021 ◽  
Vol 18 (2) ◽  
pp. 6-11
Author(s):  
A.V. Shishulin ◽  
Keyword(s):  
Curie Temperature ◽  
Mesoporous Materials ◽  
Final Section ◽  
Magnetic Phase ◽  
Pore Morphology ◽  
Model Calculations ◽  
Practical Applications ◽  
Phase Transition Temperatures ◽  
Iron Nickel ◽  
Curie Temperatures

In this paper, we have shown how the presence of pores and pore morphology influence on magnetic phase transition temperatures in mesoporous ferromagnetic materials. Model calculations have demonstrated the possibility to obtain macroscopic mesoporous samples with notably reduced Curie temperatures which is also further depressed in the case the pore morphology is more complicated. The results have been obtained on the basis of the experimentally verified correlation between the Curie temperature and cohesive energy of the material and illustrated using the examples of pure mesoporous iron, nickel and cobalt while pore morphology has been determined by the methods of fractal geometry. Several practical applications of mesoporous materials with tuned values of the Curie temperature have also been discussed in the final section.

scholarly journals Влияние структурных неоднородностей и газообразующих примесей на функциональные свойства высокочистых редкоземельных металлов

2018 ◽  
Vol 60 (6) ◽  
pp. 1103
Author(s):  
В.Б. Чжан ◽  
И.С. Терёшина
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Magnetocaloric Effect ◽  
Magnetic Phase Transition ◽  
Structural State ◽  
Magnetic Order ◽  
Magnetic Phase ◽  
Grain Sizes ◽  
Phase Transition Temperatures ◽  
Curie Temperatures

AbstractRare-earth metals (REM) gadolinium and dysprosium, and also the Gd–H and Dy–H systems in which magnetic order–order and order–disorder phase transitions are accompanied by significant magnetocaloric effect, have been studied. The materials have been prepared in various structural states. It is stated that there is a substantial difference of their functional properties in the dependence on the features of the structural state and also on the existence of a gas-forming impurity. It has been proved experimentally and theoretically that the Curie temperatures of Gd samples with grain sizes of ~200 nm increases as a result of hydrogenation, while the magnetic phase transition temperatures of Dy are almost unchanged Inhomogeneities.

scholarly journals The effects of additive on microstructure and electrical properties of batio3 ceramics

2004 ◽  
Vol 1 (3) ◽  
pp. 89-98 ◽  
Author(s):  
Vesna Paunovic ◽  
Ljiljana Zivkovic ◽  
Ljubomir Vracar ◽  
Vojislav Mitic ◽  
Miroslav Miljkovic
Keyword(s):  
Dielectric Constant ◽  
Curie Temperature ◽  
Room Temperature ◽  
Low Frequency ◽  
Dissipation Factor ◽  
The Other ◽  
Uniform Microstructure ◽  
Average Grain Size ◽  
Solid State Sintering ◽  
Curie Temperatures

In this paper comparative investigations of microstructure and dielectric properties of BaTiO3 ceramics doped with 1.0 wt% of Nb2O5, MnCO3 and CaZrO3 have been done. BaTiO3 samples were prepared using conventional method of solid state sintering at 13000C for two hours. Two distinguish micro structural regions can be observed in sample doped with Nb2O5. The first one, with a very small grained microstructure and the other one, with a rod like grains. In MnCO3 and CaZrO3 doped ceramics the uniform microstructure is formed with average grain size about 0.5- 2?m and 3-5?m respectively. The highest value of dielectric permittivity at room temperature and the greatest change of permittivity in function of temperature were observed in MnCO3/BaTiO3. In all investigated samples dielectric constant after initially large value at low frequency attains a constant value at f = 6kHz. A dissipation factor is independent of frequency greater than 10 kHz and, depending of systems, lies in the range from 0.035 to 0.25. At temperatures above Curie temperatures, the permittivity of all investigated samples follows a Curie- Weiss law. A slight shift of Curie temperature to the lower temperatures, in respect of Curie temperature for undoped BaTiO3, was observed in all investigated samples.

The Phase Transformation and Magnetic Properties in Ni-Mn-In Alloys

2013 ◽  
Vol 712-715 ◽  
pp. 54-57 ◽  
Author(s):  
Hai Le Yan ◽  
Zong Bin Li ◽  
Chun Yang Zhang ◽  
Yu Dong Zhang ◽  
Claude Esling ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Phase Transformation ◽  
Structural Transition ◽  
Alloy Composition ◽  
Ferromagnetic Shape Memory Alloys ◽  
Scanning Calorimetry ◽  
Phase Transition Temperatures ◽  
Ferromagnetic Shape Memory ◽  
Curie Temperatures ◽  
Magnetization Change

The phase transformation and magnetic properties of Heusler-type Ni50Mn50-xInx(x=10~16) ferromagnetic shape-memory alloys have been systemically investigated by differential scanning calorimetry and vibrating sample magnetometry. It is found that the phase transition temperatures show a linear relationship with the In concentration and the curie temperatures of austenite phases are not sensitive to the alloy composition. The existence of large magnetization change during the magneto-structural transition is the origin of magnetic-field-induced transformation effect.

A class of Pb-free double perovskite halide semiconductors with intrinsic ferromagnetism, large spin splitting and high Curie temperature

2018 ◽  
Vol 5 (5) ◽  
pp. 961-968 ◽  
Author(s):  
Bo Cai ◽  
Xi Chen ◽  
Meiqiu Xie ◽  
Shengli Zhang ◽  
Xuhai Liu ◽  
...  
Keyword(s):  
Curie Temperature ◽  
Double Perovskite ◽  
Spin Splitting ◽  
Ferromagnetic Semiconductors ◽  
High Curie Temperature ◽  
Intrinsic Ferromagnetism ◽  
Curie Temperatures ◽  
Large Spin

We introduce perovskite halides into spintronics, and these materials are ferromagnetic semiconductors with large spin splitting and high Curie temperatures.

scholarly journals Room-temperature multiferroicity and diversified magnetoelectric couplings in 2D materials

2019 ◽  
Vol 7 (2) ◽  
pp. 373-380 ◽  
Author(s):  
Tingting Zhong ◽  
Xiaoyong Li ◽  
Menghao Wu ◽  
Jun-Ming Liu
Keyword(s):  
First Principles ◽  
Room Temperature ◽  
2D Materials ◽  
Magnetoelectric Coupling ◽  
Alternative Possibility ◽  
Practical Applications ◽  
Layer Structures ◽  
Curie Temperatures ◽  
Ultrathin Layer ◽  
Ferroelectric Switching

Abstract Multiferroics are rare in nature due to the mutual exclusive origins of magnetism and ferroelectricity. The simultaneous coexistence of robust magnetism/ferroelectricity and strong magnetoelectric coupling in single multiferroics is hitherto unreported, which may also be attributed to their potential conflictions. In this paper, we show the first-principles evidence of such desired coexistence in ultrathin-layer CuCrS2 and CuCrSe2. The vertical ferroelectricity is neither induced by an empty d shell nor spin-driven, giving rise to an alternative possibility of resolving those intrinsic exclusions and contradictions. Compared with their bulk phases, the ferromagnetism in the thin-layer structures (two–six layers) can be greatly stabilized due to the enhanced carrier density and orbital shifting by vertical polarization, and the Curie temperatures of both ferromagnetism and ferroelectricity can be above room temperature. Moreover, a considerable net magnetization can be reversed upon ferroelectric switching, where the change in spin-resolved band structure also renders efficient ‘magnetic reading + electrical writing’. The thickness-different layers may even exhibit diversified types of magnetoelectric coupling, which both enriches the physics of multiferroics and facilitates their practical applications.

Rheological properties of cholesteric liquid crystals as lubricant additives

2019 ◽  
Vol 33 (05) ◽  
pp. 1950014 ◽  
Author(s):  
A. Bindu Madhavi ◽  
S. Sreehari Sastry
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Loss Modulus ◽  
Flow Behavior ◽  
Lubricant Additives ◽  
Rheological Parameters ◽  
Practical Applications ◽  
Phase Transition Temperatures ◽  
Frequency Independent ◽  
Temperature Shear

Rheological properties of Cholesteryl n-valerate, Cholesteryl decanoate and Cholesteryl myristate which are esters of cholesterol have been studied. Phase transition temperatures and rheological parameters such as viscosity, elastic modulus G[Formula: see text], loss modulus G[Formula: see text] as functions of temperature, shear rate and time are investigated. In frequency sweep test, a higher transition crossover region has occurred for Cholesteryl myristate, whereas for Cholesteryl n-valerate a frequency-independent plateau prevailed for both the moduli. The occurrence of blue phase in Cholesteryl decanoate during temperature sweep measurements is an indication for the rheological support. The results for steady state have informed that cholesteric esters are having non-Newtonian flow behavior in their respective cholesteric phases. The power-law model has explained well the shear rate dependence of shear stress. A few practical applications of these esters as lubricant additives are discussed, too.

The development, use and application of the gas production technique at Cornell University, USA

1998 ◽  
Vol 22 ◽  
pp. 45-54 ◽  
Author(s):  
A. N. Pell ◽  
R. E. Pitt ◽  
P. H. Doane ◽  
P. Schofield
Keyword(s):  
Logistic Model ◽  
Final Section ◽  
Linear Models ◽  
Gas Production ◽  
Production Data ◽  
Theoretical Discussion ◽  
Practical Applications ◽  
Cornell University ◽  
Freeze Dried ◽  
Digestion Kinetics

AbstractSystems to measure gas production to study digestion kinetics have been developed at several locations. The system developed at Cornell University and the rationale behind its evolution are described with an emphasis on whether venting after each observation is necessary and on choice of sensors. Different non-linear-models used to fit gas production data are discussed with an emphasis on the dual-pool logistic model. The third section of the paper includes a theoretical discussion on how gas data can be integrated with data on passage to predict ruminal digestibility. The final section addresses the practical applications of these gas data and ways in which they can be used in models like the Cornell net carbohydrate and protein system. Also included are evaluations of ensiled and freeze-dried samples from the same source as an indication of how gas systems can be used to evaluate the soluble fractions of forages.

Experimental Study of Magnetocaloric Effect in Ni-Fe-Mn-Ga and Ni-Co-Mn-Ga Heusler Alloys

2013 ◽  
Vol 738-739 ◽  
pp. 456-460 ◽  
Author(s):  
Rafael Fayzullin ◽  
Vasiliy D. Buchelnikov ◽  
Sergey Taskaev ◽  
Mikhail Drobosyuk ◽  
Vladimir V. Khovaylo
Keyword(s):  
Martensitic Transformation ◽  
Curie Temperature ◽  
Magnetocaloric Effect ◽  
Temperature Increase ◽  
Direct Method ◽  
Heusler Alloys ◽  
Iron Concentration ◽  
Magnetostructural Transition ◽  
Phase Transition Temperatures ◽  
Magnetic Field Change

In this work we experimentally studied the MCE in the Heusler alloys Ni2.19-xFexMn0.81Ga (x = 0.01, 0.02, 0.03, 0.04) and Ni2.16-xCoxMn0.84Ga (x = 0.03, 0.06, 0.09). Magnetocaloric effect was measured by the direct method using the installation from the company AMT&C. The temperature dependencies of ∆Tad for the magnetic field change ∆H = 2 T were measured. The phase transition temperatures were determined from temperature dependencies of low field magnetization measured by original setup using Hall effect. Studies have shown that replacement of the Ni atoms with the iron atoms slightly reduces the temperature magnetostructural transition for x = 0.01,0.02, and starting with x = 0.03, magnetic and structural transitions occur separately and a further increase in iron concentration leads to the Curie temperature increase, while the temperature martensitic transformation decreases. When replacing the Ni atoms with the Co atoms of the martensitic transformation temperature and Curie temperature increase.

The Magnetic Phase Transitions and Magnetocaloric Effect in the Ho(Co1-XAlx)2 and Tb(Co1-XAlx)2 Compounds

2010 ◽  
Vol 168-169 ◽  
pp. 119-121 ◽  
Author(s):  
S.A. Nikitin ◽  
G.A. Tskhadadze ◽  
I.A. Ovchenkova ◽  
D.A. Zhukova ◽  
T.I. Ivanova
Keyword(s):  
Phase Transitions ◽  
Curie Temperature ◽  
Magnetocaloric Effect ◽  
Magnetic Phase ◽  
Magnetic Ordering ◽  
Magnetic Phase Transitions ◽  
Al Content ◽  
Direct Measurements ◽  
Magnetic Ordering Temperature ◽  
Ferrimagnetic Structure

Direct measurements of the magnetocaloric effect (MCE) and magnetization have been conducted for the R(Co1-xAlx)2 (R = Tb, Ho) compounds. It was found that the small substitutions of Co by nonmagnetic Al lead to an increase both of the magnetic ordering temperature and the value of MCE. The following increase in Al content decreases the Curie temperature and the value of MCE. The analyses of the MCE effect is conducted considering the ferrimagnetic structure and the itinerant nature of these compounds.

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