scholarly journals Ferromagnetic state above room temperature in a proximitized topological Dirac semimetal

2019 ◽  
Vol 100 (24) ◽  
Author(s):  
Masaki Uchida ◽  
Takashi Koretsune ◽  
Shin Sato ◽  
Markus Kriener ◽  
Yusuke Nakazawa ◽  
...  
Keyword(s):  
Room Temperature ◽  
Ferromagnetic State ◽  
Dirac Semimetal

Room-Temperature Manipulation of Spin Texture in a Dirac Semimetal

2020 ◽  
Vol 14 (5) ◽  
Author(s):  
An-Qi Wang ◽  
Peng-Zhan Xiang ◽  
Xing-Guo Ye ◽  
Wen-Zhuang Zheng ◽  
Dapeng Yu ◽  
...  
Keyword(s):  
Room Temperature ◽  
Dirac Semimetal ◽  
Temperature Manipulation ◽  
Spin Texture

Synthesis and Magnetic Properties of CoAl2O4 Coated Co Solid Solution Nanocapsules

2010 ◽  
Vol 663-665 ◽  
pp. 1256-1259
Author(s):  
Gui Mei Shi ◽  
Ge Song ◽  
Shu Lian ◽  
Jin Bing Zhang
Keyword(s):  
Solid Solution ◽  
Photoelectron Spectrum ◽  
Room Temperature ◽  
Ferromagnetic State ◽  
Antiferromagnetic Order ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Core ◽  
New Type ◽  
The Magnetic Field

A new type of antiferromagnetic CoAl2O4 coated ferromagnetic Co solid solution is synthesized by arc-discharging. Typical HRTEM images show that the nanocapsules form in a core-shell structure. The size of the nanocapsules is in range of 10-90 nm and the thickness of the shell is about 3-10 nm. X-ray photoelectron spectrum (XPS) and X-ray diffraction (XRD) reveal that the core consists of Co solid solution, while the shell is CoAl2O4. The magnetic field and temperature dependence of magnetizations confirm that the Co solid solution nanocapsules are basically in the ferromagnetic state below Curie temperature. In addition, the antiferromagnetic order occurs with Neél temperature TN of about 5 K. The saturation magnetization of Ms = 76.1 Am2/kg and the coercive force of Hc= 23.28 kA/m are achieved at room temperature for the Co solid solution nanocapsules.

scholarly journals Tuning ferromagnetism at room temperature by visible light

2020 ◽  
Vol 117 (12) ◽  
pp. 6417-6423 ◽  
Author(s):  
Bálint Náfrádi ◽  
Péter Szirmai ◽  
Massimo Spina ◽  
Andrea Pisoni ◽  
Xavier Mettan ◽  
...  
Keyword(s):  
Room Temperature ◽  
Magnetic Moments ◽  
Ferromagnetic State ◽  
Perovskite Oxide ◽  
External Control ◽  
Digital Information ◽  
Alternative Approach ◽  
Ferromagnetic Domains ◽  
Radical Method ◽  
Oxide Perovskite

Most digital information today is encoded in the magnetization of ferromagnetic domains. The demand for ever-increasing storage space fuels continuous research for energy-efficient manipulation of magnetism at smaller and smaller length scales. Writing a bit is usually achieved by rotating the magnetization of domains of the magnetic medium, which relies on effective magnetic fields. An alternative approach is to change the magnetic state directly by acting on the interaction between magnetic moments. Correlated oxides are ideal materials for this because the effects of a small external control parameter are amplified by the electronic correlations. Here, we present a radical method for reversible, light-induced tuning of ferromagnetism at room temperature using a halide perovskite/oxide perovskite heterostructure. We demonstrate that photoinduced charge carriers from theCH3NH3PbI3photovoltaic perovskite efficiently dope the thinLa0.7Sr0.3MnO3film and decrease the magnetization of the ferromagnetic state, allowing rapid rewriting of the magnetic bit. This manipulation could be accomplished at room temperature; hence this opens avenues for magnetooptical memory devices.

scholarly journals Calculation of Ferromagnetic State and Critical Temperature in Transition Metal Doped III-V Wurtzite Semiconductors

2018 ◽  
Vol 41 (2) ◽  
pp. 217-225 ◽  
Author(s):  
MA Shamsul ◽  
M Shahjahan ◽  
MM Rahman
Keyword(s):  
Transition Metal ◽  
Room Temperature ◽  
Mean Field ◽  
Ferromagnetic State ◽  
Energy Difference ◽  
Local Magnetic Moment ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Transition Metal Atoms ◽  
Metal Doped

The magnetic properties and electronic states of the transition metal doped III-V wurtzite compounds (A1−xMx)N are calculated using Korringa-Kohn-Rostoker Green’s function method combined with the coherent potential approximation, where A = Al, Ga and M = 3d transition metal atoms namely V, Cr, Mn, Fe, Co, Ni and x is the fractional concentration of M. The positive value of the energy difference between ferromagnetic (FM) state and disordered local magnetic moment (DLM) state per unit cell denotes the magnetic phase stability. The total energy difference (EDLMEFM) is used to estimate the Curie temperature (TC) within the mean-field approximation. The calculated TC of V and Cr doped nitrides increases rapidly at lower concentrations and is found to be above the room temperature in the concentration range of x = 0.05 – 0.20. The FM behavior in Mn doped (Al1−xMnx)N is suppressed at the concentration range of x = 0.01 – 0.10. A clear phase transition from DLM to FM state occurs at concentrations x > 0.10. The energy difference in Fe, Co and Ni doped materials, results in lower values of the DLM states, where the super-exchange interaction dominates over the FM one. The FM materials exhibiting TC above room temperature have applications in the field of spintronics.Journal of Bangladesh Academy of Sciences, Vol. 41, No. 2, 217-225, 2017

Spin fluctuation scattering of neutrons and the ferromagnetic state in iron

1956 ◽  
Vol 235 (1202) ◽  
pp. 305-320 ◽  
Keyword(s):  
Theoretical Model ◽  
Room Temperature ◽  
Spin Fluctuation ◽  
Ferromagnetic State ◽  
Theory And Practice ◽  
Thermal Agitation ◽  
Electron Model ◽  
Iron Crystal ◽  
Heisenberg Type ◽  
Nuclear Amplitude

The theory and practice of neutron diffuse reflexion which has been developed in earlier papers is here applied to the question: what theoretical model of ferromagnetism is most apposite in the case of iron? Experimental results on the response of diffusely reflected intensity to the magnetization of an iron crystal at room temperature and at 907°K are interpreted as excluding the collective-electron representation, and indicating that the Heisenberg-type, localized-electron model is much closer to the truth. From the fit obtained between the observations and the predictions of the localized-electron model it is suggested that the magnetic electrons in iron vibrate under thermal agitation with measurably less than the nuclear amplitude.

scholarly journals Ferromagnetism from non-magnetic ions: Ag-doped ZnO

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Nasir Ali ◽  
Vijaya A. R. ◽  
Zaheer Ahmed Khan ◽  
Kartick Tarafder ◽  
Anuvesh Kumar ◽  
...  
Keyword(s):  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Magnetic Coupling ◽  
Ferromagnetic State ◽  
Coupling Energy ◽  
Unpaired Spin ◽  
Magnetic Ions ◽  
Doped Zno ◽  
Ferromagnetic Ordering ◽  
Magnetic Ion

AbstractTo develop suitable ferromagnetic oxides with Curie temperature (TC) at or above room temperature for spintronic applications, a great deal of research in doping ZnO with magnetic ions is being carried out over last decade. As the experimental results on magnetic ions doped ZnO are highly confused and controversial, we have investigated ferromagnetism in non-magnetic ion, Ag, doped ZnO. When Ag replaces Zn in ZnO, it adopts 4d9 configuration for Ag2+ which has single unpaired spin and suitable exchange interaction among these spins gives rise to ferromagnetism in ZnO with above room temperature TC. Experimentally, we have observed room temperature ferromagnetism (RTFM) in Ag-doped ZnO with Ag concentration varied from 0.03% to 10.0%. It is shown that zinc vacancy (VZn) enhances the ferromagnetic ordering (FMO) while oxygen vacancy (VO) retards the ferromagnetism in Ag-doped ZnO. Furthermore, the theoretical investigation revealed that VZn along with Ag2+ ions play a pivotal role for RTFM in Ag-doped ZnO. The Ag2+-Ag2+ interaction is ferromagnetic in the same Zn plane whereas anti-ferromagnetic in different Zn planes. The presence of VZn changes the anti-ferromagnetic to ferromagnetic state with a magnetic coupling energy of 37 meV. Finally, it has been established that the overlapping of bound magnetic polarons is responsible for RTFM in low doping concentration. However, anti-ferromagnetic coupling sets in at higher doping concentrations and hence weakens the FMO to a large extent.

Ferromagnetic Properties in Co-Substituted Titania Nanosheets

2008 ◽  
Vol 388 ◽  
pp. 119-122
Author(s):  
Minoru Osada ◽  
Yasuo Ebina ◽  
Kazunori Takada ◽  
Takayoshi Sasaki
Keyword(s):  
First Principles ◽  
Room Temperature ◽  
Magnetic Circular Dichroism ◽  
Room Temperature Ferromagnetism ◽  
Ferromagnetic State ◽  
Optical Measurements ◽  
Induced Anisotropy ◽  
2D System ◽  
Exhibit Room Temperature Ferromagnetism ◽  
Strong Spin

Two-dimensional (2D) Ti1-xCoxO2 nanosheet, a recently discovered ferromagnic nanomaterial, has been investigated by magnetic and magneto-optical measurements. The multilayer films of Ti0.8Co0.2O2 nanosheets exhibit room-temperature ferromagnetism with magnetic moment of 1.4 μ B/Co. We also observe robust magnetic circular dichroism near the absorption edge at 4 eV, indicating a strong spin polarization in this 2D system. The first-principles study of Ti1-xCoxO2 nanosheet characterizes the ferromagnetic state with a spin-orbit-induced anisotropy.

scholarly journals Carbothermal reduction of mill scales formed on steel billets during continuous casting

2021 ◽  
Vol 242 (1) ◽  
Author(s):  
S. M. Espinoza Suarez ◽  
L. E. Borja-Castro ◽  
M. I. Valerio-Cuadros ◽  
A. Bustamante Domínguez ◽  
H. A. Cabrera-Tinoco ◽  
...  
Keyword(s):  
Iron Oxides ◽  
Carbothermal Reduction ◽  
Room Temperature ◽  
Reduction Process ◽  
Ferromagnetic State ◽  
Argon Atmosphere ◽  
X Ray Diffraction ◽  
Spectroscopy Analysis ◽  
Crude Steel ◽  
X Ray

AbstractA billet is a bar made from crude steel which surface contains scales which are rich in iron oxides. This study presents the carbothermal reduction of the scales formed in steel billets. The process included the reaction of the iron oxides contents with carbon (in ratio 5:1) and annealing in a tubular furnace under argon atmosphere. The occurred reactions are discussed using thermodynamic calculations and thermal analysis which indicate a three-stage reduction process Fe3O4 ➔ FeO ➔ Fe3C ➔α-Fe with intermediate reactions at the interval temperature 960 and 1300 °C. The X-ray diffraction confirms the reduction to α-Fe with minor presence of unreacted C, magnetite and wustite. Mössbauer spectroscopy analysis was performed at room temperature where a typical sextet corresponding to the dominant α-Fe is shown as well as wustite, magnetite and cementite to a lesser extent. The magnetization measurements confirm the ferromagnetic state corresponding to the α-Fe.

Y-Type Hexaferrites: Structural, Dielectric and Magnetic Properties

2012 ◽  
Vol 189 ◽  
pp. 209-232 ◽  
Author(s):  
Rajshree B. Jotania ◽  
Hardev Singh Virk
Keyword(s):  
Magnetic Properties ◽  
Quantum Interference ◽  
Room Temperature ◽  
Structural Changes ◽  
Ferromagnetic State ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Lcr Meter ◽  
Co Precipitation

This paper attempts to provide a historical survey of structure of various types of hexaferrites. It provides information about synthesis, characterization, structural, magnetic and dielectric properties of Y-type hexagonal ferrites using various chemical routes. We have prepared a series of cobalt doped Sr2Cu2-xCoxFe12O22(x = 0.0 to 1.0) hexaferrites using a wet chemical co-precipitation technique. The prepared hexaferrite precursors were calcined at 950 °C for 4 hours in a furnace and slowly cooled to room temperature. The crystal structure of Y-type hexaferrites is rather complicated. The chemical and structural changes were examined in detail by X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Scanning electron microscopy (SEM), and Fourier transform infra-red (FTIR) spectroscopy. X-ray diffraction studies showed that sintering temperature as low as 950°C was sufficient to produce a single-phase Y-type hexaferrite material. The dielectric measurements were carried out over the frequency range of 100 Hz to 2 MHz at room temperature using an LCR meter to study the variation of dielectric constant and loss tangent with frequency. The magnetic properties of hexaferrite samples were investigated using a vibration sample magnetometer (VSM), and a superconducting quantum interference device (SQUID) magnetometer in the temperature range 30K to 200K. A change from ferromagnetic state to super paramagnetic state has been observed in Co doped Sr2Cu2-xCoxFe12O22(x= 0.6 to 1.0) hexaferrite. The novel applications of all types of hexaferrite materials have been described.

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