Effects of Sn, Co and Fe on MgB2

Kühberger, Markus; Gritzner, G.

doi:10.1016/s0921-4534(01)01130-3

Cited by 56 publications

(39 citation statements)

References 5 publications

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“…Similar behavior of c͑x͒ and a͑x͒ was reported for Al-substituted crystals, 31 and for Co-and Cr-substituted polycrystalline materials. 38,40 The distinct con- traction of the MgB 2 unit cell along the c-axis observed for our substituted crystals indicates that Mn enters the crystal structure. Similar conclusion has been also derived from the single crystal x-ray investigations where it was possible to refine the Mg 1−x Mn x B 2 structure with Mn on Mg position only.…”

Section: Resultsmentioning

confidence: 79%

“…In spite of this great experimental and theoretical effort, the superconducting and normal-state properties of MgB 2 substituted with magnetic ions have been investigated briefly and in polycrystalline materials. [37][38][39][40] Concomitantly to this work, the Mn-substituted MgB 2 crystals from the same batches have been studied by a pointcontact spectroscopy. 41 In our previous studies we have reported on the crystallographic and superconducting properties of MgB 2 single crystals substituted with Al and C ions.…”

Section: Introductionmentioning

confidence: 99%

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Strong magnetic pair breaking in Mn-substitutedMgB2single crystals

et al. 2006

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Magnetic ions ͑Mn͒ were substituted in MgB 2 single crystals resulting in a strong pair-breaking effect. The superconducting transition temperature, T c , in Mg 1−x Mn x B 2 has been found to be rapidly suppressed at an initial rate of 10 K / % Mn, leading to a complete suppression of superconductivity at about 2% Mn substitution. This reflects the strong coupling between the conduction electrons and the 3d local moments, predominantly of magnetic character, since the nonmagnetic ion substitutions, e.g., with Al or C, suppress T c much less effectively ͑e.g., 0.5 K / % Al͒. The magnitude of the magnetic moment ͑Ӎ1.7 B per Mn͒, derived from normal state susceptibility measurements, uniquely identifies the Mn ions to be divalent, and to be in the low-spin state ͑S =1/2͒. This has been found also in x-ray absorption spectroscopy measurements. Isovalent Mn 2+ substitution for Mg 2+ mainly affects superconductivity through spin-flip scattering reducing T c rapidly and lowering the upper critical field anisotropy H c2 ab / H c2 c at T = 0 from 6 to 3.3 ͑x = 0.88% Mn͒, while leaving the initial slope dH c2 /dT near T c unchanged for both field orientations.

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Section: Resultsmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Strong magnetic pair breaking in Mn-substitutedMgB2single crystals

et al. 2006

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“…The endothermic peak at 650 °C corresponds to melting of magnesium. The exothermic peak at 570 °C corresponds to creation of MgB 2 in solid-solid reaction [32]. The two merged peaks above 730 °C correspond to formation of new phases.…”

Section: Reaction Of Ni-co-b Nanoparticles With Precursor Powdermentioning

confidence: 97%

Enhancing superconducting properties of MgB₂pellets by addition of amorphous magnetic Ni–Co–B nanoparticles

Mustapić

Horvat

Hossain

et al. 2013

Supercond. Sci. Technol.

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Amorphous magnetic Ni-Co-B nanoparticles with an average size of 5 nm were added to precursor powders of MgB2 superconductor. The preparation procedure for MgB2 pellets was optimized for obtaining the best critical current density ( Jc) at elevated magnetic fields. Addition of Ni-Co-B decreases the Jc for heat treatment of precursor powders at 650 ° C. Heat treatments at 770 ° C and higher improve Jc at 20 and 5 K. This improvement occurs at both temperatures through the increase of the effective connectivity between MgB2 crystals. Vortex pinning was enhanced at 5 K, but not at 20 K. Ni-Co-B nanoparticles reacted with Mg in heat treatments above 730 ° C, forming Mg2Ni and MgCo2 nanoparticles. Ni-Co-B addition was associated with lower oxygen content in MgB2, indicating that reduction of MgO content is the mechanism for improvement of grain connectivity. Decomposition of magnetic Ni-Co-B nanoparticles results mostly in nonmagnetic nanoparticles, so magnetic pinning did not occur in our samples.

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“…On the other hand enormous efforts are made to improve the superconducting properties of MgB 2 so that it can be brought on the platform of application. In order to achieve the enhanced properties, as in case of cuprate superconductors, the range of different substituents such as Al, Li, Si, Zr, Cu [13], Sc [14][15][16], Nb, Mn, Fe, Sn, Co [17], Ni, Ag, Au [18], Ca [19] at Mg sites and C, Be [20], F [21], Cr [22] at B sites, were tried. Out of these, only for Zn doping the transition temperature increased or nearly remained the same [23,24]; otherwise the rest of them led to a considerable decrease in T c .…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Carbon-Doped MgB2 Superconductor Under Inert Carbon Environment

Sinha

Chung

Pawar

et al. 2011

J Supercond Nov Magn

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A systematic study on the synthesis of carbondoped MgB 2 superconductor, using a new approach wherein the sample was treated under both pressed carbon environment as well as flowing argon, is presented. The sample synthesized was found to be compact and showed cannibalistic surface morphology. Carbon doping in the sample, crystallized in hexagonal structure, accounted for the reduced inplane lattice parameter of 3.06 Å. The intraband scattering due to doping of carbon resulted in a decreased superconducting transition at about 29 K. The behavior of resistivity with respect to a decrease in temperature was embedded in the signatures for the scattering of electrons by phonons as well as the grain boundary impurity in the sample. The carbon doping achieved by the proposed synthesis technique showed improvement in the self-field critical current density up to around 10 5 A/cm 2 at 5 K. The flux-pinning plots were studied to understand the dominant pinning mechanism in the sample.

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Effects of Sn, Co and Fe on MgB2

Cited by 56 publications

References 5 publications

Strong magnetic pair breaking in Mn-substitutedMgB2single crystals

Strong magnetic pair breaking in Mn-substitutedMgB2single crystals

Enhancing superconducting properties of MgB₂pellets by addition of amorphous magnetic Ni–Co–B nanoparticles

Synthesis and Characterization of Carbon-Doped MgB2 Superconductor Under Inert Carbon Environment

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Effects of Sn, Co and Fe on MgB2

Cited by 56 publications

References 5 publications

Strong magnetic pair breaking in Mn-substitutedMgB2single crystals

Strong magnetic pair breaking in Mn-substitutedMgB2single crystals

Enhancing superconducting properties of MgB2pellets by addition of amorphous magnetic Ni–Co–B nanoparticles

Synthesis and Characterization of Carbon-Doped MgB2 Superconductor Under Inert Carbon Environment

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Enhancing superconducting properties of MgB₂pellets by addition of amorphous magnetic Ni–Co–B nanoparticles