Temperature dependence of transport spin polarization in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Nd</mml:mi><mml:msub><mml:mi mathvariant="normal">Ni</mml:mi><mml:mn>5</mml:mn></mml:msub></mml:mrow></mml:math>from point-contact Andreev reflection

Mukhopadhyay, Sourin; Raychaudhuri, Pratap; Joshi, Devang A.; Tomy, C. V.

doi:10.1103/physrevb.75.014504

Cited by 22 publications

(34 citation statements)

References 40 publications

(47 reference statements)

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“…The resistivity, ρ , of the amorphous NdNi 5 (from now on called a-NdNi 5 ) thin films is measured from room temperature down to T = 4.2 K, using a van der Pauw configuration 20 . Previous studies, on single crystals or polycrystalline NdNi 5 samples 8,11 , show pronounced anomalies in the resistivity at T ∼ 7.2 K, close to the magnetic ordering temperature 10 . However, differences in the transport properties originate from the loss of periodic arrangement.…”

Section: Resultsmentioning

confidence: 81%

“…Also negative values of α are observed. However, in the case of magnetic systems this happens in a small range of T, of the order of few Kelvin, close to the magnetic transition 8,11,23 . In the case of magnetic amorphous alloys this behavior, studied by means of electron-transport measurements, is attributed to weak-localization (WL) www.nature.com/scientificreports/ effects [24][25][26] rather than to Kondo mechanism, which is related to the presence of localized magnetic impurities in the system 27 .…”

Section: Resultsmentioning

confidence: 99%

“… crystallizes in a -type hexagonal structure (space group P 6/ mmm ) 10 with lattice parameters and 8 , 10 . X-ray diffraction traces on polycrystalline show their highest-intensity peaks at = for the (101) diffraction and at = for the (111) diffraction 8 . The thin films investigated in this study are amorphous, as determined through high resolution X-ray diffraction (XRD) measurements performed in grazing incident configuration.…”

Section: Resultsmentioning

confidence: 99%

“…In order to be used in conjunction with superconductors such as Nb ( K, T c is the superconducting transition temperature) or NbN ( K), the most frequently used materials in superconducting electronics, it is crucial to realize good quality thin films because their availability may enable the design of dedicated transport experiments based on heterostructures operating as S/F-based devices. However, currently is only available in crystal form 8 , 11 , 12 and, to the best of our knowledge, thin films have not been fabricated. Furthermore, it would be useful to obtain non-crystalline films since amorphous magnetic materials are typically characterized by narrow hysteresis loops.…”

Section: Introductionmentioning

confidence: 99%

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Magnetotransport and magnetic properties of amorphous $$\mathrm{NdNi}_5$$ thin films

Cirillo

Barone

Bradshaw

et al. 2020

Sci Rep

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NdNi 5 is an intermetallic compound with a bulk Curie temperature (T Curie) of 6-13 K. While existing studies have focused on NdNi 5 crystals, amorphous thin-films of NdNi 5 are potentially important since they would be magnetically soft without magnetocrystalline anisotropy, meaning that small external magnetic fields could reverse the direction of their magnetization. Here, we report NdNi 5 thin-films with a thickness in the 5-200 nm range, deposited by DC magnetron sputtering onto Si(100). Films are amorphous with a weak temperature-dependent resistivity with values ranging between 150 and 300 µ cm. By means of noise spectroscopy, by analyzing the time-dependence of fluctuationinduced voltages, it is found that at low temperatures the resistance fluctuations are due to the Kondo effect. Volume magnetometry indicates T Curie = 70 K with a magnetic coercive field of 30 mT at 5 K for a 125-nm-thick film. The results are promising for the development of Ferromagnet(F)/ Superconductor(S)/Ferromagnet(F) pseudo spin-valve devices based on amorphous NdNi 5 thin films. Spintronics is a major field of research in condensed matter physics 1. The capability to create and manipulate electronic spin currents enables to realize spin-based devices which, compared to their traditional charge-based counterpart, can be faster and demand lower power 1. The birth of spintronics traces back to the discovery of giant magnetoresistance (GMR) in Fe/Cr synthetic antiferromagnetic multilayers in which the electrical resistance increases when the magnetization in the magnetic layers changes from a parallel to an antiparallel alignment 2,3. A large number of material systems have been proposed for spintronics 4 including superconductors in conjunction with magnetic materials. This has paved the way for superconducting spintronics, which has potential to lead to the development of circuits that are more energy efficient, meaning that they should generate less heat and require low power for their functioning 5,6. In particular, a ferromagnet with a small value of the coercive field, H c , can be easily tuned in its magnetic properties, going from a state in which the magnetization, M, is zero when the applied external magnetic field H is equal to H c to a state in which, for H > H c , M = 0. In superconducting/ ferromagnetic (S/F) systems, this property can push the S/F system from the normal to superconducting state at low temperatures. Such a system can be used as a superconducting valve, since it can be switched between a superconducting (ON) and a normal (OFF) state by controlling the value of H. NdNi 5 is an intermetallic compound belonging to the RENi 5 (RE = Rare-earth) series. In bulk form, it is characterized by a large magnetocrystalline anisotropy, with the easy (hard) axis lying along the a axis within the hexagonal plane (the c axis) and an a axis (c axis) magnetization at 35 T of 3.3 μ B /f.u. (1.65 μ B /f.u.) 7,8 , and a T Curie in the range of 6-13 K 8-11. Here μ B is the Bohr magneton. In order to be used in conjunction wit...

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Section: Resultsmentioning

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetotransport and magnetic properties of amorphous $$\mathrm{NdNi}_5$$ thin films

Cirillo

Barone

Bradshaw

et al. 2020

Sci Rep

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“…The finite lifetime of the Cooper pairs has been used to describe the spectra of non-magnetic contacts [11], but with few exceptions [8,9,12] it has not generally been applied to contacts with magnetic metals even though one should expect strong pair breaking in that case. Since spectra of both magnets and non-magnets can often be fitted rather well with the two models, we have suggested…”

Section: Introductionmentioning

confidence: 99%

Spin polarization versus lifetime effects at point contacts between superconducting niobium and normal metals

Tuuli

Gloos

2012

J. Phys.: Conf. Ser.

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Abstract. Point-contact Andreev reflection spectroscopy is used to measure the spin polarization of metals but analysis of the spectra has encountered a number of serious challenges, one of which is the difficulty to distinguish the effects of spin polarization from those of the finite lifetime of Cooper pairs. We have recently confirmed the polarization-lifetime ambiguity for NbCo and Nb-Cu contacts and suggested to use Fermi surface mismatch, the normal reflection due to the difference of Fermi wave vectors of the two electrodes, to solve this dilemma. Here we present further experiments on contacts between superconducting Nb and the ferromagnets Fe and Ni as well as the noble metals Ag and Pt that support our previous results. Our data indicate that the Nb -normal metal interfaces have a transparency of up to about 80% and a small, if not negligible, spin polarization. IntroductionWith the growing interest in spintronics, measuring the spin polarization P of a metal has become an important task [1]. Andreev reflection spectroscopy of point contacts has been suggested as an effective and versatile technique for measuring the polarization of metals in contact with a superconductor [2,3]. To extract the polarization, one analyses the measured differential resistance spectra with the help of a modified BTK model [4,5,6]. This method has been applied to a wide range of materials, delivering converging values for the spin polarization. The extracted P has a linear or parabolic dependence on the relative strength of the interface barrier Z, and the true value of the polarization P is measured in the Z = 0 limit. Unfortunately, this procedure has also encountered problems, including inadequately understood additional spectral features [7] and, most of all, the degeneracy of the results of the various BTK type models [8,9]. This applies especially when the polarization is low.We have recently demonstrated how difficult it is to distinguish the effects of polarization and finite lifetime of Cooper pairs in the spectra of Nb-Co and Nb-Cu contacts [10]. The finite lifetime of the Cooper pairs has been used to describe the spectra of non-magnetic contacts [11], but with few exceptions [8,9,12] it has not generally been applied to contacts with magnetic metals even though one should expect strong pair breaking in that case. Since spectra of both magnets and non-magnets can often be fitted rather well with the two models, we have suggested

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Efficient Thermo‐Spin Conversion in van der Waals Ferromagnet FeGaTe

Liu,

Hu,

Cui

et al. 2023

Advanced Materials

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Recent discovery of 2D van der Waals magnetic materials has spurred progress in developing advanced spintronic devices. A central challenge lies in enhancing the spin‐conversion efficiency for building spin‐logic or spin‐memory devices. Here, the anomalous Hall and Nernst effects are systematically investigated to uncover significant spin‐conversion effects in above‐room‐temperature van der Waals ferromagnet FeGaTe with perpendicular magnetic anisotropy. The anomalous Hall effect demonstrates an efficient electric spin‐charge conversion with a notable spin Hall angle of over 6%. In addition, the anomalous Nernst effect produces a significant transverse voltage at room temperature without a magnetic field, displaying unique temperature dependence with a maximum transverse Seebeck coefficient of 440 nV K−1 and a Nernst angle of ≈62%. Such an innovative thermoelectric signal arises from the efficient thermo‐spin conversion effect, where the up‐spin and down‐spin electrons move in opposite directions under a temperature gradient. The present study highlights the potential of FeGaTe to enhance thermoelectric devices through efficient thermo‐spin conversion without the need for a magnetic field.

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Temperature dependence of transport spin polarization inNdNi5from point-contact Andreev reflection

Cited by 22 publications

References 40 publications

Magnetotransport and magnetic properties of amorphous $$\mathrm{NdNi}_5$$ thin films

Magnetotransport and magnetic properties of amorphous $$\mathrm{NdNi}_5$$ thin films

Spin polarization versus lifetime effects at point contacts between superconducting niobium and normal metals

Efficient Thermo‐Spin Conversion in van der Waals Ferromagnet FeGaTe

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