The magnetic Curie temperature and exchange coupling between cations in tetragonal spinel oxide Mn2.5M0.5O4 (M = Co, Ni, Mn, Cr, and Mg) films

2012 ◽  
Vol 111 (7) ◽  
pp. 07A507 ◽  
Author(s):  
K. Kuo ◽  
C. W. Cheng ◽  
G. Chern
Keyword(s):  
Curie Temperature ◽  
Exchange Coupling ◽  
Spinel Oxide ◽  
Tetragonal Spinel

scholarly journals PROXIMITY EFFECTS AND CURIE TEMPERATURE ENHANCEMENT IN Co/EuS AND Fe/EuS MULTILAYERS

SPIN ◽  
2012 ◽  
Vol 02 (04) ◽  
pp. 1250016 ◽  
Author(s):  
B. LEWITZ ◽  
A. STRAUB ◽  
V. KAPAKLIS ◽  
P. POULOPOULOS ◽  
A. DELIMITIS ◽  
...  
Keyword(s):  
Curie Temperature ◽  
Exchange Coupling ◽  
Proximity Effects ◽  
Antiferromagnetic Exchange ◽  
Coupling Constant ◽  
Polycrystalline Structure ◽  
Individual Layer ◽  
Temperature Enhancement ◽  
The Individual ◽  
Almost Continuous

Two identical Co/EuS and Fe/EuS multilayers of six periods each and with individual layers of about 4 nm thick are grown by e-beam evaporation under ultrahigh vacuum conditions. The films show polycrystalline structure with a grain size limited by the individual layer thickness. Both multilayers consist of almost continuous layers with some roughness. The surface peak-to-peak roughness is about 4–5 nm. Magnetization measurements and calculations of the loops based on a Stoner–Wohlfarth-like model allow us to determine the direct antiferromagnetic exchange coupling constant between the 3d metal and EuS at 5 K. Both samples show strong enhancement of the Curie temperature of EuS up to at least 50 K with a EuS magnetization tail, which persists up to about 100 K. The J = 7/2 character of the EuS layers is shown to be responsible for the large Curie temperature enhancement.

scholarly journals EXCHANGE COUPLING AND ENHANCEMENT OF CURIE TEMPERATURE OF THE INTERGRANULAR AMORPHOUS REGION IN NANO-CRYSTALLINE DUPLEX-PHASE ALLOYS SYSTEM

2007 ◽  
Vol 21 (27) ◽  
pp. 4689-4706
Author(s):  
Y. Z. SHAO ◽  
W. R. ZHONG ◽  
G. M. LIN ◽  
X. D. HU
Keyword(s):  
Curie Temperature ◽  
Exchange Coupling ◽  
Volume Fraction ◽  
Amorphous Region ◽  
Experimental Result ◽  
Dual Phase ◽  
Two Phase ◽  
Nanocrystallite Size ◽  
Nano Crystalline ◽  
Two Component

We studied the theoretical Curie temperature of a dual-phase nanomagnetic system by Monte Carlo simulation of a modified Heisenberg model on a 3D complex lattice consisting of single- and cluster-spins. We also systematically investigated the experimental Curie temperature of a dual-phase nanomagnetic alloy and performed a direct comparison between theory and experiment. The exchange coupling between two component magnetic phases substantially affects the Curie temperature [Formula: see text] of the intergranular amorphous region of a dual-phase nanomagnetic system. The [Formula: see text] depends upon the nanocrystallite size d, the volume fraction Vc and the interspace among crystallites ξ. Large crystallized volume fraction Vc, small grain size d, and thin interphase thickness ξ lead to an obvious enhancement of Curie temperature (ECT) of intergranular amorphous region, whereas the Curie temperature of nanocrystallites [Formula: see text] decreases slightly. By simulation, we worked out a relationship between the reduced ECT and ξ, as [Formula: see text], and it conforms to the experimental result. In addition, we also simulated the demagnetization of a hard–soft nanocomposite system. The exchange coupling between two component phases affects the cooperativity of two-phase magnetizations, the coherent reversal of magnetizations, and coercivity.

Effect of Interlayer Exchange Coupling on the Curie Temperature in Ga1-xMnxAs Trilayer Structures

2003 ◽  
Author(s):  
Sh.U. Yuldashev ◽  
Yongmin Kim ◽  
Nayoung Kim ◽  
Hyunsik Im ◽  
T.W. Kang ◽  
...  
Keyword(s):  
Curie Temperature ◽  
Exchange Coupling ◽  
Interlayer Exchange Coupling ◽  
Interlayer Exchange

Effect of Interlayer Exchange Coupling on the Curie Temperature in Ga1-xMnxAs Trilayer Structures

2004 ◽  
Vol 43 (4B) ◽  
pp. 2093-2096 ◽  
Author(s):  
Shavkat U. Yuldashev ◽  
Yongmin Kim ◽  
Nayoung Kim ◽  
Hyunsik Im ◽  
Tae Won Kang ◽  
...  
Keyword(s):  
Curie Temperature ◽  
Exchange Coupling ◽  
Interlayer Exchange Coupling ◽  
Interlayer Exchange

A STUDY ON MAGNETIC PROPERTIES OF Cu-DOPED GaN

2011 ◽  
Vol 25 (17) ◽  
pp. 1457-1472 ◽  
Author(s):  
LI-BIN SHI ◽  
HONG-KUAN YUAN
Keyword(s):  
Magnetic Properties ◽  
Curie Temperature ◽  
Exchange Coupling ◽  
Density Functional ◽  
Coupling Model ◽  
Weak Ferromagnetism ◽  
First Principle ◽  
Theoretical Understanding ◽  
Functional Theory ◽  
Carbon Impurities

Using the first principle method based on density functional theory (DFT), we have studied the magnetic properties in Cu -doped GaN . The result shows that Cu in GaN exhibits spontaneous spin polarization. The energies of ferromagnetism (FM) and antiferromagnetism (AFM) coupling are calculated for eleven different configurations. It is found that Cu -doped GaN has a FM ground state. It is not found that Cu atoms have a clear clustering tendency. Origin of FM properties is also explained by energy level coupling model. In the paper, we also investigate the effect of nitrogen, gallium vacancies and carbon impurities on magnetic properties. The results show that nitrogen, gallium vacancies and carbon impurities cannot enhance FM coupling of Cu -doped GaN . In addition, exchange coupling coefficient and Curie temperature are also investigated. The Cu -doped GaN is proposed to be weak ferromagnetism according to Curie temperature and magnetic moment. The present study provides some theoretical understanding for the experiments on Cu -doped GaN .

Temperature Dependence of Strong Exchange Coupling in Ferrite Heterostructures

1997 ◽  
Vol 475 ◽  
Author(s):  
Y. Suzuki ◽  
R.B. Van Dover ◽  
R.J. Felder
Keyword(s):  
Thin Film ◽  
Curie Temperature ◽  
Temperature Dependence ◽  
Coercive Field ◽  
Exchange Coupling ◽  
Spinel Structure ◽  
Room Temperature ◽  
Blocking Temperature ◽  
Soft Layer ◽  
Strong Exchange

ABSTRACTSingle crystalline spinel structure ferrite thin film bilayers exhibit nearly ideal exchange coupling at room temperature. In these bilayers, the blocking temperature is only limited by the Curie temperature of the (Mn,Zn)Fe2O4. Up to the Curie temperature of the soft (Mn,Zn)Fe2O4 layer, the magnetization loops indicate that exchange anisotropy dominates the magnetization of the soft layer up to magnetic fields on the order of the coercive field of the hard CoFe2O4layer.

The Effect of Doping Fe on Magnetic Property of Colossal Magnetoresistance of La0.7Sr0.3MnO3 Materials

2014 ◽  
Vol 644-650 ◽  
pp. 4860-4863
Author(s):  
Bao He Li ◽  
Ping Ping Xiang
Keyword(s):  
Magnetic Properties ◽  
Magnetic Property ◽  
Curie Temperature ◽  
Electric Conductivity ◽  
Exchange Coupling ◽  
Colossal Magnetoresistance ◽  
Sol Gel ◽  
Ferromagnetic Property ◽  
Ferromagnetic Exchange ◽  
Gel Technique

Colossal magnetoresistance of La0.7Sr0.3MnO3compounds (x=0~0.18) were prepared by the sol-gel technique. Partial Mn atoms were replaced by Fe atoms and its influence on the structure, magnetic properties and colossal magnetoresistance were also studied. Our results show that the Curie temperature decreases fast, the ferromagnetic property is weakened, the electric conductivity is decreased and the colossal magnetoresistance is enhanced as an increase of replacing Mn by Fe atoms. It was convinced by the theory of molecular field that doping Fe atoms can decrease the ferromagnetic exchange coupling of La0.7Sr0.3MnO3

Positron Annihilation Studies on La1-xSrxMnO3 Manganites

2017 ◽  
Vol 373 ◽  
pp. 201-204
Author(s):  
Yu Yang Huang ◽  
Yan Meng ◽  
Wen Hua Huang ◽  
Shou Lei Xu ◽  
Ding Kang Xiong ◽  
...  
Keyword(s):  
Curie Temperature ◽  
Positron Annihilation ◽  
Electron Density ◽  
Exchange Coupling ◽  
Positron Lifetime ◽  
Double Exchange ◽  
Ferromagnetic Coupling ◽  
Doppler Broadening ◽  
Doppler Broadening Spectra ◽  
Coincidence Doppler Broadening

Positron lifetime and coincidence Doppler broadening spectra of La1-xSrxMnO3 and LaMnO3 manganites were measured. The effects of Sr contents on the microdefects of La1-xSrxMnO3 were investigated by means of positron lifetime results. The signals of 3d electrons of La1-xSrxMnO3 were extracted from the coincidence Doppler broadening spectra. The results show that the electron density of La1-xSrxMnO3 is larger than that of LaMnO3. The open volume of the defect in La1-xSrxMnO3 increases with the Sr contents. The signals of 3d electrons of ferromagnetic La1-xSrxMnO3 is larger than that of antiferromagnetic LaMnO3, and it reaches the maximum at x=0.33, that is, the signals of 3d electrons of the La0.67Sr0.33MnO3 is the highest in all testing samples, which corresponds to a lowest resistivity and a higher Curie temperature of the manganite. The influence of 3d electrons on the ferromagnetic double-exchange coupling and anti-ferromagnetic coupling of La1-xSrxMnO3 were discussed.

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