Anomalous Magnetism in Eu(Ca)B6

2009 ◽  
Vol 152-153 ◽  
pp. 307-310 ◽  
Author(s):  
V.V. Glushkov ◽  
M.A. Anisimov ◽  
A.V. Bogach ◽  
S.V. Demishev ◽  
N.A. Samarin ◽  
...  
Keyword(s):  
Experimental Data ◽  
Magnetic Properties ◽  
Curie Temperature ◽  
Single Crystals ◽  
Carrier Density ◽  
Double Exchange ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Paramagnetic Curie Temperature ◽  
Magnetoresistive Effect

The transport and magnetic properties of the Eu1-xCaxB6 (0x0.4) single crystals were studied in the wide ranges of temperatures (1.8-300 K) and magnetic fields (up to 8 T). The experimental data allow to identify a metal-insulator transition (MIT) at the critical Ca concentration xMIT≈0.3, which agrees well with the predictions of double exchange model (V.M. Pereira et al. Phys. Rev. Lett., 93 (2004) 147202). A significant enhancement of magnetoresistive effect is observed below 100K for Eu1-xCaxB6 compounds corresponding to the metallic side of the MIT (xxMIT). The drastic decrease of paramagnetic Curie temperature evaluated from the magnetic and magnetotransport data is discussed in terms of quantum MIT scenario recently proposed for this low carrier density system.

Suppression of Ferromagnetism in EuxCa1-xB6

2012 ◽  
Vol 190 ◽  
pp. 97-100 ◽  
Author(s):  
V.V. Glushkov ◽  
A.V. Kuznetsov ◽  
I. Sannikov ◽  
A.V. Bogach ◽  
S.V. Demishev ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Susceptibility ◽  
Curie Temperature ◽  
Single Crystals ◽  
Effective Magnetic Moment ◽  
Paramagnetic State ◽  
Low Field ◽  
Wide Range ◽  
Free Ion ◽  
The Eu

We report the magnetic properties of EuxCa1-xB6 single crystals (0.756x1) studied in the wide range of temperatures (1.8-300 K) and magnetic fields (up to 50 kOe). It was found that low field magnetic susceptibility χ (T) follows the Curie-Weiss law χ~(T-Θp)-1 at high temperatures for all the concentrations studied. The effective magnetic moment of the Eu2+ ion estimated from the data diminishes from the free ion value μeff7.93μB (μB - Bohr magneton) for x=1 to μeff7.3μB for x=0.756. A universal behavior of magnetic susceptibility χ~(T-Θ)-α (α=1.5) is detected close to the Curie temperature TC in the paramagnetic state at both metallic (x>xC~0.8) and dielectric (xC.

Magnetic properties of undoped and Co-doped n-type β–FeSi2.5 single crystals

2002 ◽  
Vol 17 (11) ◽  
pp. 2960-2965 ◽  
Author(s):  
E. Arushanov ◽  
L. Ivanenko ◽  
D. Eckert ◽  
G. Behr ◽  
U. K. Rößler ◽  
...  
Keyword(s):  
Activation Energy ◽  
Magnetic Properties ◽  
Magnetic Susceptibility ◽  
External Field ◽  
Single Crystals ◽  
Spin Glasses ◽  
Paramagnetic Centers ◽  
Temperature Dependent ◽  
Paramagnetic Curie Temperature ◽  
Co Doped

Results of magnetization and magnetic susceptibility measurements on undoped and Co-doped FeSi2.5 single crystals are presented. The temperature dependence of the magnetic susceptibility of the Co-doped sample in the range of 5–300 K can be explained by temperature-dependent contributions due to paramagnetic centers and the carriers excited thermally in the extrinsic conductivity region. The values of the paramagnetic Curie temperature and activation energy of the donor levels were estimated. It is also shown that the magnetic susceptibility of Co-doped samples cooled in zero external field and in a field are different. This resembles the properties of spin-glasses and indicates the presence of coupling between magnetic centers.

Contribution to the study of the metal-insulator transition in the system II. Magnetic properties

1972 ◽  
Vol 11 (1) ◽  
pp. vii
Author(s):  
J.P. Pouget ◽  
P. Lederer ◽  
D.S. Schreiber ◽  
H. Launois ◽  
D. Wohlleben ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator

Magnetic properties across the metal‐insulator transition (invited)

1988 ◽  
Vol 63 (8) ◽  
pp. 4285-4290 ◽  
Author(s):  
Subir Sachdev ◽  
R. N. Bhatt ◽  
M. A. Paalanen
Keyword(s):  
Magnetic Properties ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator

Magnetic properties and the metal–insulator transition in solid solutions

2010 ◽  
Vol 150 (13-14) ◽  
pp. 602-604 ◽  
Author(s):  
O.B. Romanova ◽  
L.I. Ryabinkina ◽  
V.V. Sokolov ◽  
A.Yu. Pichugin ◽  
D.A. Velikanov ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Solid Solutions ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator

Magnetic, Electronic - and Magneto - Transport Properties of Nanocrystalline Nd0.6Sr0.4MnO3 Manganites

2009 ◽  
Vol 67 ◽  
pp. 131-136 ◽  
Author(s):  
Kundu Sourav ◽  
Kumar Nath Tapan
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Transition Temperature ◽  
Curie Temperature ◽  
Transport Properties ◽  
Significant Variation ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Low Field

We have reported in this paper, the effect of grain size in Nd0.6Sr0.4MnO3 .We have investigated the effect of grain size on metal-insulator transition and Curie temperature. We have also reported here the variation of low field magnetoresistance with temperature and grain size. We have observed that the Curie temperature increases monotonically with particle size. The metal insulator transition temperature initially increases with particle size and then gets fixed to a certain value. In these Nd0.6Sr0.4MnO3 nanometric systems, any significant variation of magnetoresistance with particle size is not observed.

The Behavior of the Spin-One-Half Falicov–Kimball Model Close to the Metal–Insulator Transition

1998 ◽  
Vol 12 (26) ◽  
pp. 2709-2716 ◽  
Author(s):  
Pavol Farkašovský
Keyword(s):  
Experimental Data ◽  
Electrical Conductivity ◽  
Exact Diagonalization ◽  
Two Dimensions ◽  
Insulator Transition ◽  
Rare Earth Compounds ◽  
Qualitative Explanation ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Exhaustive Study

The spin-one-half Falicov–Kimball model for electronically driven valence and metal–insulator transitions is studied in one and two dimensions using small-cluster exact-diagonalization calculations. Performing an exhaustive study of the model close to the metal–insulator transition we have found that the spin-one-half Falicov–Kimball model can describe much of experimental data of transition-metal and rare-earth compounds. Particularly, except the discontinuous transitions it can provide the qualitative explanation for all typical behaviors of the electrical conductivity observed experimentally in these materials.

Effect of uniaxial pressure on metal-insulator transition in (Sm1−yNdy)0.52Sr0.48MnO3 single crystals

2009 ◽  
Vol 94 (25) ◽  
pp. 252506 ◽  
Author(s):  
A. Murugeswari ◽  
P. Sarkar ◽  
S. Arumugam ◽  
N. Manivannan ◽  
P. Mandal ◽  
...  
Keyword(s):  
Single Crystals ◽  
Insulator Transition ◽  
Uniaxial Pressure ◽  
Metal Insulator Transition ◽  
Metal Insulator

Grain-Size Effects and the Physical Properties of La0.7Ca0.3MnO3-δ

2005 ◽  
Vol 277-279 ◽  
pp. 929-934 ◽  
Author(s):  
H.K. Lee ◽  
Horst Baier ◽  
J.S. Park ◽  
Y.P. Lee ◽  
Youn Seoung Lee
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Transition Temperature ◽  
Physical Properties ◽  
Size Effects ◽  
Annealing Temperature ◽  
Oxygen Deficiency ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Grain Sizes

The effects of grain-size in La0.7Ca0.3MnO3-δ (LCMO) system have been studied in connection with the magnetic and electronic properties. LCMO system prepared by the solid-state reaction was annealed in air at 1200, 1300 and 1400°C. The grain sizes of LCMO samples become larger with increasing of annealing temperature (TA ). The magnetization in LCMO samples increased while the coercive field decreased with increasing TA. The conductivity increased and the metal-insulator transition temperature TM-I decreased with increasing of TA. These physical properties are due to the oxygen deficiency caused by the increase of grain size. Finally, it was found that the grain size and the mechanical connection between grains play an important role in determining the electronic and magnetic properties.

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