Critical Current Suppression in Spin-Filter Josephson Junctions
- PDF / 1,321,154 Bytes
- 7 Pages / 595.224 x 790.955 pts Page_size
- 78 Downloads / 255 Views
ORIGINAL PAPER
Critical Current Suppression in Spin-Filter Josephson Junctions Halima Giovanna Ahmad1,2 · Luigi Di Palma1 · Roberta Caruso1 · Avradeep Pal3 · Giovanni Piero Pepe1,2 · Mark G. Blamire4 · Francesco Tafuri1,2 · Davide Massarotti2,5 Received: 18 May 2020 / Accepted: 12 June 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Ferromagnetic Josepshon junctions (SFS JJs) are the basic cell of an intense research activity that extends to spintronics. The simultaneous presence of low-dissipative behavior and spin-filtering properties in JJs composed of ferro-insulating barriers (SIf S JJs) suggests their possible implementation in dissipationless versions of spintronics devices. Here, we establish a direct correlation between the suppression of the critical current in the experimental I–V curves of SIf S JJs and the spinpolarization factor derived in terms of the tunneling amplitudes for spin up and down carriers. A modelling of the JJs in terms of the Tunnel Junction Microscopic model allows to provide the scaling of the suppression parameter as a function of the barrier thickness. Keywords Josephson effect · Spintronics · Ferromagnetic Josephson junctions
1 Introduction SFS JJs are unique platforms for the study of the interplay between superconductivity and ferromagnetism [1, 2]. Tunnel ferromagnetic JJs fall in the underdamped regime with high values of the characteristic voltage Ic RN , being Ic the critical current and RN the normal resistance of the JJ [3– 6], and have the potential to offer additional functionalities in spintronics devices [2, 7–9] and in superconducting quantum and classical circuits [10, 11], including cryogenic memories compatible with SFQ logic [12–14] and active elements in quiet flux-qubits [15, 16]. In this work, we focus Halima Giovanna Ahmad
[email protected]
on the study of spin-polarization phenomena in NbN-GdNNbN spin-filter JJs and, in particular, on their influence on the suppression of the critical current Ic [17, 18]. The spin-filtering effect in SIf S heterostructures is due to the simultaneous presence of tunnel transport mechanisms and ferromagnetic ordering in the barrier [17]. An energyband splitting occurs at temperatures below the Curie temperature (TCurie ), causing the formation of unbalanced spin-currents [17]. Below Tc , spin-polarization phenomena induce a suppression of the Ic of the device [17, 19]. The possibility to study samples with different barrier thicknesses (from 1.5 to 4.0 nm) gives self-consistent criteria for the correlation between the Ic suppression and the spin-polarization factor. Here, we will show that the Ic suppression can be estimated by fitting the experimental current-voltage (I-V) characteristics by using the Tunnel Junction Microscopic (TJM) model [20–23]. Comparison with theoretical predictions of the suppression parameter confirms a general consistency of the fitting procedure, thus suggesting that small deviations, observed at extreme conditions where very strong spin-polarizat
Data Loading...
