scholarly journals Effect of Controlled Artificial Disorder on the Magnetic Properties of EuFe2(As1-xPx)2 Ferromagnetic Superconductor

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3267
Author(s):  
Sunil Ghimire ◽  
Marcin Kończykowski ◽  
Kyuil Cho ◽  
Makariy A. Tanatar ◽  
Daniele Torsello ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Irradiation Dose ◽  
Proton Irradiation ◽  
Exchange Interactions ◽  
Superconducting Phase ◽  
Superconducting Transition ◽  
Magnetic Susceptibilities ◽  
Pristine Sample ◽  
Artificial Disorder ◽  
Different Doses

Static (DC) and dynamic (AC, at 14 MHz and 8 GHz) magnetic susceptibilities of single crystals of a ferromagnetic superconductor, EuFe2(As1−xPx)2 (x = 0.23), were measured in pristine state and after different doses of 2.5 MeV electron or 3.5 MeV proton irradiation. The superconducting transition temperature, Tc(H), shows an extraordinarily large decrease. It starts at Tc(H=0)≈24K in the pristine sample for both AC and DC measurements, but moves to almost half of that value after moderate irradiation dose. Remarkably, after the irradiation not only Tc moves significantly below the FM transition, its values differ drastically for measurements at different frequencies, ≈16 K in AC measurements and ≈12 K in a DC regime. We attribute such a large difference in Tc to the appearance of the spontaneous internal magnetic field below the FM transition, so that the superconductivity develops directly into the mixed spontaneous vortex-antivortex state where the onset of diamagnetism is known to be frequency-dependent. We also examined the response to the applied DC magnetic fields and studied the annealing of irradiated samples, which almost completely restores the superconducting transition. Overall, our results suggest that in EuFe2(As1−xPx)2 superconductivity is affected by local-moment ferromagnetism mostly via the spontaneous internal magnetic fields induced by the FM subsystem. Another mechanism is revealed upon irradiation where magnetic defects created in ordered Eu2+ lattice act as efficient pairbreakers leading to a significant Tc reduction upon irradiation compared to other 122 compounds. On the other hand, the exchange interactions seem to be weakly screened by the superconducting phase leading to a modest increase of Tm (less than 1 K) after the irradiation drives Tc to below Tm. Our results suggest that FM and SC phases coexist microscopically in the same volume.

Changes in Microwave Absorbtion of New High Tc Superconductors with Small Magnetic Fields

1987 ◽  
Vol 99 ◽  
Author(s):  
K. Khachaturyan ◽  
E. R. Weber ◽  
P. Tejedor ◽  
A. Stacy ◽  
A. Portis
Keyword(s):  
Magnetic Fields ◽  
Superconducting Phase ◽  
Superconducting Transition ◽  
High Tc Superconductors ◽  
High Tc ◽  
Low Field ◽  
Flux Trapping ◽  
Field Dependent ◽  
Exponential Decrease ◽  
Stochastic Oscillations

ABSTRACTA low field microwave absorbtion peak was observed with an EPR spectrometer in the new superconducting oxides‥ The peak disappeared above the superconducting transition temperature after exponential decrease with temperature in the transition region. The peak was sensitive to the magnetic fields the sample has been exposed before in the superconducting phase. Magnetic field dependent stochastic oscillations of the EPR baseline are ascribed to flux trapping in Josephson junctions.

scholarly journals Enhancing Superconductivity of the Nonmagnetic Quasiskutterudites by Atomic Disorder

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5830
Author(s):  
Andrzej Ślebarski ◽  
Maciej M. Maśka
Keyword(s):  
High Temperature ◽  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
High Temperature Superconductors ◽  
Superconducting Phase ◽  
Length Scale ◽  
Superconducting Transition ◽  
Atomic Disorder ◽  
Strong Inhomogeneity ◽  
Related Compounds

We investigated the effect of enhancement of superconducting transition temperature Tc by nonmagnetic atom disorder in the series of filled skutterudite-related compounds (La3M4Sn13, Ca3Rh4Sn13, Y5Rh6Sn18, Lu5Rh6Sn18; M= Co, Ru, Rh), where the atomic disorder is generated by various defects or doping. We have shown that the disorder on the coherence length scale ξ in these nonmagnetic quasiskutterudite superconductors additionally generates a non-homogeneous, high-temperature superconducting phase with Tc⋆>Tc (dilute disorder scenario), while the strong fluctuations of stoichiometry due to increasing doping can rapidly increase the superconducting transition temperature of the sample even to the value of Tc⋆∼2Tc (dense disorder leading to strong inhomogeneity). This phenomenon seems to be characteristic of high-temperature superconductors and superconducting heavy fermions, and recently have received renewed attention. We experimentally documented the stronger lattice stiffening of the inhomogeneous superconducting phase Tc⋆ in respect to the bulk Tc one and proposed a model that explains the Tc⋆>Tc behavior in the series of nonmagnetic skutterudite-related compounds.

Effects of High-Energy Ball Milling Time on the Sintering Process of FeSe Superconductors

2016 ◽  
Vol 848 ◽  
pp. 657-663 ◽  
Author(s):  
Sheng Nan Zhang ◽  
Xiao Bo Ma ◽  
Ji Xing Liu ◽  
Jian Qing Feng ◽  
Cheng Shan Li ◽  
...  
Keyword(s):  
Phase Composition ◽  
Ball Milling ◽  
Optimal Parameter ◽  
High Energy ◽  
Superconducting Phase ◽  
High Energy Ball Milling ◽  
Superconducting Transition ◽  
Sintering Process ◽  
Energy Ball ◽  
Precursor Powders

FeSe superconducting bulks were prepared with high energy ball milling (HEBM) aided sintering process, within which process, tetragonal β-FeSe superconducting phase could be formed directly with one step sintering process, and the formation of hexagonal δ-FeSe non-superconducting phase was effectively avoided. The influences of HEBM time on the sintering process of FeSe bulks were systematically investigated. With different HEBM time, the phase composition and morphology of precursor powders changed correspondingly, which thus influenced the final phase composition and superconducting properties of FeSe superconducting bulks. Due to the formation of FeSe bulks with larger tetragonal phase content and higher superconducting transition temperature, HEBM time of 6.0 h was recognized as the optimal parameter. Shorter HEBM time could lead to the insufficient decrease of particle size and low density. While longer HEBM time caused the formation of amorphous hexagonal δ-FeSe, which crystallized during sintering process. Thus no more tetragonal FeSe could be obtained. The FeSe superconducting bulk with the critical temperature Tc(onset) of 8.0 K was obtained with the HEBM time of 6 h, and sintering temperature of 700 oC for 12 h.

Field-induced superconductivity in MoS2

2013 ◽  
Vol 1549 ◽  
pp. 79-84
Author(s):  
Y. J. Zhang ◽  
J. T. Ye ◽  
Y. Iwasa
Keyword(s):  
Carrier Density ◽  
Gate Dielectric ◽  
Superconducting Phase ◽  
Common Mechanism ◽  
Continuous Control ◽  
Superconducting Transition ◽  
Charge Accumulation ◽  
Density Region ◽  
2D Semiconductors ◽  
Type Conduction

ABSTRACTWe fabricated MoS2 transistor adopting electric double layer (EDL) as gate dielectric. So far, EDL has realized p-type conducting MoS2 in addition to well-known n-type conduction showing ambipolar operation. In our study, field-effect superconducting transition of MoS2 was realized with maximum TC around 10 K. This TC is the highest not only within MoS2 compounds but also among whole TMDs. The highest TC discovered in this study lies in the carrier density region much smaller than chemically investigated region. Such compounds with small doping level have never been successfully synthesized by chemical method. Furthermore, by combining HfO2 (typical high-k material for FETs) gating with EDL gating, continuous control of carrier density, and thus quantum phase, was demonstrated. As a result, we successfully obtained the phase diagram of MoS2. Interestingly, the TC exhibits strong carrier density dependence, showing dome-shaped superconducting phase. Superconducting dome in other materials than cuprates has been reported only a few times in doped 2D semiconductors. Since FET charge accumulation is basically two dimensional, our result implies the existence of common mechanism for superconducting dome in 2D band insulators.

Probe of the Band Structure of MBE Grown p-Type InMnAs at Ultrahigh Magnetic Fields

SPIN ◽  
2015 ◽  
Vol 05 (01) ◽  
pp. 1550002 ◽  
Author(s):  
Y. Sun ◽  
F. V. Kyrychenko ◽  
G. D. Sanders ◽  
C. J. Stanton ◽  
G. A. Khodaparast ◽  
...  
Keyword(s):  
Optical Properties ◽  
Magnetic Fields ◽  
Band Structure ◽  
Heavy Hole ◽  
Theoretical Calculations ◽  
Interaction Strength ◽  
Golden Rule ◽  
Exchange Interactions ◽  
Landau Levels ◽  
P Type

We present a theoretical and experimental study on electronic and magneto-optical properties of p-type paramagnetic InMnAs dilute magnetic semiconductor (DMS) alloys in ultrahigh (> 100 T) external magnetic fields (B). Theoretical calculations are based on an 8-band Pidgeon–Brown model which is generalized to include the wavevector dependence of the electronic states along B as well as s–d and p–d exchange interactions with localized Mn d-electrons. The spin-dependent electronic structure as a function of Mn doping is computed and the dependence of the valence band structure on parameters such as the sp–d exchange interaction strength and effective masses in paramagnetic p- InMnAs alloys are examined. The cyclotron resonance (CR) and magneto-optical properties of InMnAs are calculated using Fermi's golden rule. Two strong CR peaks are observed in p-type InMnAs alloys which correspond to the transitions within either heavy-hole (HH) or light-hole (LH) Landau levels. Furthermore, we also observed strong resonance absorption for electron-active polarization which can occur in p-type semiconductors originating from transitions between the light and heavy hole Landau levels.

scholarly journals Strong suppression of the resistivity near the superconducting transition in narrow microbridges in external magnetic fields

2020 ◽  
Vol 101 (6) ◽  
Author(s):  
Xiaofu Zhang ◽  
Adriana E. Lita ◽  
Konstantin Smirnov ◽  
HuanLong Liu ◽  
Dong Zhu ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Superconducting Transition ◽  
Strong Suppression

Exchange interactions in CdMnTe/CdMgTe quantum wells under high magnetic fields

2002 ◽  
Vol 13 (2-4) ◽  
pp. 568-571
Author(s):  
T Yasuhira ◽  
K Uchida ◽  
Y.H Matsuda ◽  
N Miura ◽  
S Kuroda ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Quantum Wells ◽  
Exchange Interactions ◽  
High Magnetic Fields

HEAT-TREATMENT INFLUENCE ON THE MAGNETIC AND ELECTRIC PROPERTIES OF HIGH-TcYBa2Cu3O7−δ SUPERCONDUCTOR

1996 ◽  
Vol 10 (20) ◽  
pp. 955-961
Author(s):  
LAUREAN HOMORODEAN ◽  
IULIU POP ◽  
ION BURDOI
Keyword(s):  
Heat Treatment ◽  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Room Temperature ◽  
Liquid Nitrogen Temperature ◽  
Superconducting Phase ◽  
Superconducting Transition ◽  
Temperature Dependences ◽  
Magnetic And Electric Properties ◽  
Very High

The changes in the temperature dependences of the magnetic susceptibility and the electrical resistivity of a very-high-T c superconducting YBa 2 Cu 3 O 7−δ sample during the thermal cycling between the liquid-nitrogen temperature and the room temperature are studied. Some singularities corresponding to the superconducting transition, the possible existence of a super-high-temperature superconducting phase and the migration of the oxygen atoms in the Cu-O chains are emphasized on these dependencies.

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