scholarly journals The inverted hysteresis loops and exchange bias effects in amorphous/nanocrystalline Fe72Cu1V4Si15B8 ribbons at room temperature

2020 ◽  
Vol 52 (3) ◽  
pp. 283-298
Author(s):  
Radoslav Surla ◽  
Nebojsa Mitrovic ◽  
Milica Vasic ◽  
Dragica Minic
Keyword(s):  
Hysteresis Loop ◽  
Exchange Bias ◽  
Room Temperature ◽  
Structural Changes ◽  
Annealing Temperature ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Nanocrystalline Structure ◽  
Bias Field ◽  
Thermally Induced

?he influence of thermally induced microstructural transformations on magnetic properties of Fe72Cu1V4Si15B8 ribbon with combined amorphous/nanocrystalline structure is presented. The experiments showed that thermally induced structural changes are in correlation with the appearance of magnetic hysteresis, i.e. with inverted hysteresis loops (IHL) and exchange bias (EB) effects. It was found that the ratio of surface to volume of a ribbon sample have an influence on hysteresis loop appearance. The inverted hysteresis loops were observed for the 1.5 mm wide and 55 ?m thick alloy samples shorter than 10 mm, but for the samples longer than 10 mm hysteresis loops were normal. With an increase of annealing temperature, a shift of the hysteresis loops measured at room temperature was noticed. The highest positive exchange bias field Heb was observed for the sample annealed at 723 K, together with the lowest magnetic field at which the changes from inverted to normal hysteresis loop occurred. Annealing at the temperature of 823 K resulted in negative Heb.

Exchange Bias Properties in Bulk Ni45Co5Mn38Sn12 Heusler Alloy

2014 ◽  
Vol 875-877 ◽  
pp. 272-276 ◽  
Author(s):  
Chao Jing ◽  
Ye Jun Yang ◽  
Dong Hua Yu ◽  
Zhe Li ◽  
Xiao Long Wang ◽  
...  
Keyword(s):  
Hysteresis Loop ◽  
Exchange Bias ◽  
Heusler Alloy ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Bias Field ◽  
Magnetic Hysteresis Loop ◽  
Zero Field ◽  
Co Substitution ◽  
Exchange Bias Field

We report the exchange bias properties in the bulk Ni45Co5Mn38Sn12quaternary Heusler alloy. The ferromagnetic (FM) –antiferromagnetic (AFM) interactions get reinforced after the Co substitution for Ni in the Ni-Mn-Sn alloy, which increase the exchange bias field (HE). A maximum shift in hysteresis loops of 306 Oe was observed in the 10 kOe field cooled sample. The origin of this large exchange bias field has been discussed. Magnetic hysteresis loop obtained in the zero field cooled (ZFC) mode shows double-shifted loop, and the reason of this phenomenon has been explained in detail.

scholarly journals Asymmetric Hysteresis Loops in Co Thin Films

2020 ◽  
Vol 5 (4) ◽  
pp. 71
Author(s):  
Andrea Ehrmann ◽  
Tomasz Blachowicz
Keyword(s):  
Exchange Bias ◽  
Kerr Effect ◽  
Room Temperature ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Blocking Temperature ◽  
Optical Kerr Effect ◽  
Thin Film System ◽  
Magnetic Hysteresis Loops ◽  
Magneto Optical Kerr Effect

Asymmetric magnetic hysteresis loops are usually found in exchange bias (EB) systems, typically after field cooling a system below the Néel temperature of an antiferromagnet exchange coupled to a ferromagnet. Alternatively, asymmetric hysteresis loops may occur due to undetected minor loops or in systems with a rotational anisotropy. Here, we report on an exchange bias thin film system MgO(100)/Co/CoO, examined at room temperature, which is far above the blocking temperature, by the magneto-optical Kerr effect (MOKE). While the longitudinal hysteresis loops partly show steps which are well-known from diverse purely ferromagnetic systems, the transverse hysteresis loops exhibit clear asymmetries, similar to exchange biased systems at low temperatures, and unusual transverse magnetization values at saturation. Since minor loops and a rotational anisotropy can be excluded in this case, this asymmetry can possibly be a residue of the exchange bias coupling at lower temperatures.

Structural Changes of UHV Deposited Titanium Thin Films in Presence of Oxygen Flow and Temperature

2011 ◽  
Vol 110-116 ◽  
pp. 1094-1098
Author(s):  
Haleh Kangarlou ◽  
Mehdi Bahrami Gharahasanloo ◽  
Akbar Abdi Saray ◽  
Reza Mohammadi Gharabagh
Keyword(s):  
Room Temperature ◽  
Structural Changes ◽  
Annealing Temperature ◽  
Annealing Process ◽  
Oxygen Flow ◽  
Glass Substrates ◽  
Annealing Temperatures ◽  
Titanium Thin Films ◽  
Deposition Angle ◽  
Ti Films

Ti films of same thickness, and near normal deposition angle, and same deposition rate were deposited on glass substrates, at room temperature, under UHV conditions. Different annealing temperatures as 393K, 493K and 593K with uniform 8 cm3/sec, oxygen flow, were used for producing titanium oxide layers. Their nanostructures were determined by AFM and XRD methods. Roughness of the films changed due to annealing process. The gettering property of Ti and annealing temperature can play an important role in the nanostructure of the films.

scholarly journals Exchange bias in ferromagnetic bilayers with orthogonal anisotropies: the case of GaMnAsP/GaMnAs combination

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Suho Choi ◽  
Seul-Ki Bac ◽  
Xinyu Liu ◽  
Sanghoon Lee ◽  
Sining Dong ◽  
...  
Keyword(s):  
Exchange Bias ◽  
Easy Axis ◽  
Initial Conditions ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
The Other ◽  
Planar Hall Effect ◽  
Magnetic Layers ◽  
Out Of Plane ◽  
Magnetic Hysteresis Loops

Abstract We report the observation of exchange bias in a ferromagnetic Ga0.94Mn0.06As0.77P0.23/ Ga0.94Mn0.06As bilayer, in which the easy axis in one layer is oriented out-of-plane, and in the other in-plane. Magnetization reversal in this system is explored using planar Hall effect (PHE) measurements under various initial conditions and with various field-cooling orientations. Our results show that the two magnetic layers are ferromagnetically exchange-coupled, and that such coupling results in pronounced exchange-bias-like shifts of magnetic hysteresis loops during reversal of in-plane magnetization. The presence of exchange bias in this system can be understood on the basis of magnetic closure domains formed in the layer with the out-of-plane easy axis.

scholarly journals Ferroelectric and Magnetic Properties of Hot-Pressed BiFeO3-PVDF Composite Films

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Annapu V. Reddy ◽  
K. C. Sekhar ◽  
Navneet Dabra ◽  
A. Nautiyal ◽  
Jasbir S. Hundal ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Coercive Field ◽  
Polyvinylidene Fluoride ◽  
Room Temperature ◽  
Magnetic Hysteresis ◽  
Composite Films ◽  
Hysteresis Loops ◽  
Liquid Phase Sintering ◽  
Magnetic Hysteresis Loops ◽  
Ferroelectric Hysteresis

The ferroelectric and magnetic properties of hot-pressed BiFeO3- (BFO) polyvinylidene fluoride (PVDF) composite films have been studied. The BiFeO3 (BFO) ceramics have been synthesized by a rapid liquid phase sintering technique. The X-ray diffraction (XRD) studies revealed that the impure phase observed in pure BFO ceramics was significantly reduced in the composite films. The presence of both ferroelectric and magnetic hysteresis loops confirms the multiferroic nature of the composite films at room temperature. A well-saturated ferroelectric hysteresis loop with a remanent polarization (Pr)∼4.8 μC-cm-2 and coercive field (Ec)∼1.55 kV/cm has been observed in composite thin films at room temperature. The magnetic hysteresis loops were traced at room temperature with SQUID. The remanent magnetization (Mr)∼3.0×10−3 emu/gm and coercive field (Hc)∼0.99 kOe was observed in the composite film. The magnetic polarization of the composite films has found to be enhanced as compared to pure BFO and correlated to reduction in BFO impure peak intensity.

Magnetoresistance of Nanoscale Domain Walls Formed in Arrays of Parallel Nanowires

SPIN ◽  
2019 ◽  
Vol 09 (01) ◽  
pp. 1950004
Author(s):  
Jingchun Wang ◽  
Floriano Cuccureddu ◽  
Rafael Ramos ◽  
Cormac Ó. Coileáin ◽  
Igor V. Shvets ◽  
...  
Keyword(s):  
Thin Films ◽  
Domain Wall ◽  
Exchange Interaction ◽  
Exchange Bias ◽  
Room Temperature ◽  
Domain Walls ◽  
Nanowire Array ◽  
Bias Field ◽  
Nanowire Arrays ◽  
Exchange Bias Field

We present the possibility of enhancing magnetoresistance (MR) by controlling nanoscale domain wall (DW) width in a planar nanowire array. Results based on micromagnetic calculations show that DW width decreases with increasing exchange bias field and decreases with reducing exchange interaction between neighboring nanowires. Fe/Fe3O4 nanowire arrays were grown on [Formula: see text]-plane sapphire to demonstrate the feasibility of this concept, and an enhanced MR ratio of 3.7% was observed at room temperature. compared with flat and stepped Fe3O4 thin films.

scholarly journals Inspection of Reactor Steel Degradation by Magnetic Adaptive Testing

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 963
Author(s):  
Gábor Vértesy ◽  
Antal Gasparics ◽  
Ildikó Szenthe ◽  
Ferenc Gillemot ◽  
Inge Uytdenhouwen
Keyword(s):  
Structural Changes ◽  
Magnetic Measurements ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Charpy Impact ◽  
Adaptive Testing ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Type Definition ◽  
Magnetic Adaptive Testing

Degradation of nuclear pressure vessel steel materials, 15Kh2NMFA type and A508 Cl2 type (definition is given in the text) were investigated by a novel magnetic nondestructive testing method, so-called Magnetic Adaptive Testing (MAT), which is based on systematic measurement and evaluation of minor magnetic hysteresis loops. The measured samples were thermally treated by a special step cooling procedure, which generated structural changes in the material. It was found that this type of degradation can be easily followed by magnetic measurements. Charpy impact test were also performed and the results were compared with the magnetic parameters. In case of 15Kh2NMFA steel, a good, reliable and closely linear correlation was found between magnetic descriptors and transition temperature.

Oscillatory Angular Dependence of Exchange Bias for Epitaxial NiO-Co (001) Bilayers

2001 ◽  
Vol 674 ◽  
Author(s):  
S. Dubourg ◽  
J.F. Bobo ◽  
B. Warot ◽  
E. Snoeck ◽  
J.C. Ousset
Keyword(s):  
Magnetic Field ◽  
Exchange Bias ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Field Application ◽  
Zero Field ◽  
Sign Change ◽  
Realistic Description ◽  
Sputter Deposited ◽  
The Magnetic Field

ABSTRACTWe have sputter-deposited NiO-Co bilayers on MgO (001) substrates. NiO grows epitaxially on MgO at 900°C and subsequently the room deposited 80 Åthick Co films have a fcc crystal structure in epitaxy with the oxide underlayer. These samples were warmed up to 300° C and then zero-field or field cooled through the NiO Néel temperature (a 300 Oe magnetic field was applied along the [100] or the [110] MgO axis). Magnetic hysteresis loops were obtained by magneto-optical Kerr effect, the magnetic field being oriented in the plane of the substrate for various angles α with respect to the [100] direction. The usually expected behavior for such experiments is a smooth angular α dependence of the exchange bias HE close to a cosine with only one sign change over 180°. The high crystallographic coherence of our NiO/Co bilayers induces a very unusual oscillatory HE (α) dependence with several sign changes according to the NiO axis field application. Despite of the Co magnetization switching mechanism which is not a pure coherent rotation, we propose a Stoner-Wohlfhart model including four fold anisotropy and unidirectional exchange anisotropy giving a realistic description of these typical magnetic properties.

A Dissipative Quantum Dynamic Approach to Magnetic Hysteresis Loop and Magnetization Relaxation for Molecule Magnet Mn12

2003 ◽  
Vol 17 (17) ◽  
pp. 3215-3224
Author(s):  
Yuanchang Su ◽  
Yongjin Jiang
Keyword(s):  
Hysteresis Loop ◽  
Time Evolution ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Magnetic Hysteresis Loop ◽  
Quantum Dynamic ◽  
Magnetization Relaxation ◽  
Resonant Tunnelling ◽  
State Evolution ◽  
Different Temperatures

A new approach to the magnetic hysteresis loop and magnetization relaxation of molecule magnet, Mn12, is presented. The method, so called "quasi-thermal equilibrium (QTE) + erase phase (EP)" (QTE + EP), leads the dissipation in state evolution. The method gives an method to approach an irreversible quantum dynamic tunnelling and time evolution of system and straightly leads the hysteresis loops. The QTE can work well for the double-well system and is able to be extended to the multi-wells quantum system. The EP is based on the physics of random interaction with the environment that results the phase de-coherence or say "re-initial" of the phase of quantum state during the time evolution. The stairs in the magnetic loops of Mn12 we have obtained quantitatively show the quantum resonant tunnelling. The relaxation of magnetization from initial lowest state is calculated for different temperatures and well shows the exponential behavior. The theoretical results well agree with the experiments.

The Influence of CeO2-Doping of Nanosized Cadmium Ferrite on Catalytic Conversion of Ethanol

2020 ◽  
Vol 13 (2) ◽  
pp. 156-169
Author(s):  
Abdelrahman A. Badawy ◽  
Ahmed M. Rashad ◽  
Shaimaa M. Ibrahim ◽  
Sahar M. El-Khouly
Keyword(s):  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Magnetic Hysteresis ◽  
Maximum Yield ◽  
Hysteresis Loops ◽  
Ethanol Conversion ◽  
Ferrite Formation ◽  
Opposite Trend ◽  
Magnetic Hysteresis Loops

Background: The role of CeO2-doping (0.75-3 mol%) and calcination temperature on solid-solid interaction between ferric and cadmium oxides yielding cadmium ferrites was examined. Methods and Results: The results exposed that ceria improves the ferrite formation by heating at 600-700ºC via the dissolution of some dopant cation in the lattice of CdO with the subsequent creation of anionic vacancies and/or formation of higher valency cadmium cation (Cd(2+δ)+). SBET of solids calcined at 500oC increased by CeO2-doping, while opposite trend for solids calcined at 600 and 700oC. The magnetic hysteresis loops of all samples showed room-temperature ferromagnetism with different hysteresis loop shapes. Conclusion: Magnetization increased by CeO2-doping that might be due to the enhancement of cadmium ferrite formation. Ethanol conversion increased by increasing CeO2-doping. Dehydrogenation product (acetaldehyde) was mainly the yield of ethanol conversion. The maximum yield of acetaldehyde (92.97%) carried out for solids doped with 3 mol% CeO2.

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