Electric field control of magnetic properties and electron transport in BaTiO3-based multiferroic heterostructures

In this paper, we report on a purely electric mechanism for achieving the electric control of the interfacial spin polarization and magnetoresistance in multiferroic tunneling junctions. We investigate micrometric devices based on the Co/Fe/BaTiO3/La0.7Sr0.3MnO3 heterostructure, where Co/Fe and La0.7Sr0.3MnO3 are the magnetic electrodes and BaTiO3 acts both as a ferroelectric element and tunneling barrier. We show that, at 20 K, devices with a 2 nm thick BaTiO3 barrier present both tunneling electroresistance (TER = 12   ±   0.1%) and tunneling magnetoresistance (TMR). The latter depends on the direction of the BaTiO3 polarization, displaying a sizable change of the TMR from  -0.32   ±   0.05% for the polarization pointing towards Fe, to  -0.12   ±   0.05% for the opposite direction. This is consistent with the on-off switching of the Fe magnetization at the Fe/BaTiO3 interface, driven by the BaTiO3 polarization, we have previously demonstrated in x-ray magnetic circular dichroism experiments

Magneto-ionic effect in CoFeB thin films with in-plane and perpendicular-to-plane magnetic anisotropy

The magneto-ionic effect is a promising method to control the magnetic properties electrically. Charged mobile oxygen ions can easily be driven by an electric field to modify the magnetic anisotropy of a ferromagnetic layer in contact with an ionic conductor in a solid-state device. In this paper, we report on the room temperature magneto-ionic modulation of the magnetic anisotropy of ultrathin CoFeB films in contact with a GdOxlayer, as probed by polar micro-Magneto Optical Kerr Effect during the application of a voltage across patterned capacitors. Both Pt/CoFeB/GdOxfilms with perpendicular magnetic anisotropy and Ta/CoFeB/GdOxfilms with uniaxial in-plane magnetic anisotropy in the as-grown state exhibit a sizable dependence of the magnetic anisotropy on the voltage (amplitude, polarity, and time) applied across the oxide. In Pt/CoFeB/GdOxmultilayers, it is possible to reorient the magnetic anisotropy from perpendicular-to-plane to in-plane, with a variation of the magnetic anisotropy energy greater than 0.2 mJ m-2. As for Ta/CoFeB/GdOxmultilayers, magneto-ionic effects still lead to a sizable variation of the in-plane magnetic anisotropy, but the anisotropy axis remains in-plane

Evidence for spin to charge conversion in GeTe(111)

GeTe has been predicted to be the father compound of a new class of multifunctional materials, ferroelectric Rashba semiconductors, displaying a coupling between spin-dependent k-splitting and ferroelectricity. In this paper, we report on epitaxial Fe/GeTe(111) heterostructures grown by molecular beam epitaxy. Spin-pumping experiments have been performed in a radio-frequency cavity by pumping a spin current from the Fe layer into GeTe at the Fe ferromagnetic resonance and detecting the transverse charge current originated in the slab due to spin-to-charge conversion. Preliminary experiments indicate that a clear spin to charge conversion exists, thus unveiling the potential of GeTe for spin-orbitronics

Chronic kidney disease progression and outcome according to serum phosphorus in mild-to-moderate kidney dysfunction

BACKGROUND AND OBJECTIVES: Several factors might alter serum phosphate homeostasis and induce hyperhosphatemia in patients with chronic kidney disease (CKD) not requiring dialysis. However, whether and to what extent hyperphosphatemia is associated with a poor prognosis in different CKD patient groups remain to be elucidated. DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS: We utilized the "Prevenzione Insufficienza Renale Progressiva" (PIRP) database, a large project sponsored by the Emilia-Romagna Health Institute. PIRP is a collaborative network of nephrologists and general practitioners located in the Emilia-Romagna region, Italy, aimed at increasing awareness of CKD complications and optimizing CKD patient care. We identified 1716 patients who underwent a GFR and serum phosphorous assessment between 2004 and 2007. We tested whether phosphate levels 654.3 mg/dl are associated with the risk of CKD progression or all causes of death. RESULTS: Older age and male sex were associated with lower phosphate levels. Instead, higher phosphate levels were noted in patients with diabetes. Patients with phosphate levels 654.3 mg/dl were at an increased risk of starting dialysis or dying (hazard ratio 2.04; 95% confidence interval [1.44, 2.90]). Notably, subgroup analyses revealed that the magnitude of the risk associated with hyperphosphatemia varied depending on age, sex, diabetes, and different stages of CKD. CONCLUSIONS: These analyses lend support to the hypothesis that phosphorous abnormalities might have a negative effect on the residual renal function and prognosis in different groups of CKD patients. However, the risk associated with hyperphosphatemia might vary in specific CKD patient subgroups

Electrically controlled long-distance spin transport through an antiferromagnetic insulator

Spintronics uses spins, the intrinsic angular momentum of electrons, as an alternative for the electron charge. Its long-term goal is in the development of beyond-Moore low dissipation technology devices. Recent progress demonstrated the long-distance transport of spin signals across ferromagnetic insulators. Antiferromagnetically ordered materials are however the most common class of magnetic materials with several crucial advantages over ferromagnetic systems. In contrast to the latter, antiferromagnets exhibit no net magnetic moment, which renders them stable and impervious to external fields. In addition, they can be operated at THz frequencies. While fundamentally their properties bode well for spin transport, previous indirect observations indicate that spin transmission through antiferromagnets is limited to short distances of a few nanometers. Here we demonstrate the long-distance, over tens of micrometers, propagation of spin currents through hematite (\alpha-Fe2O3), the most common antiferromagnetic iron oxide, exploiting the spin Hall effect for spin injection. We control the spin current flow by the interfacial spin-bias and by tuning the antiferromagnetic resonance frequency with an external magnetic field. This simple antiferromagnetic insulator is shown to convey spin information parallel to the compensated moment (N\'eel order) over distances exceeding tens of micrometers. This newly-discovered mechanism transports spin as efficiently as the net magnetic moments in the best-suited complex ferromagnets. Our results pave the way to ultra-fast, low-power antiferromagnet-insulator-based spin-logic devices that operate at room temperature and in the absence of magnetic fields

Strain induced shape anisotropy in antiferromagnetic structures

We demonstrate how shape dependent strain can be used to control antiferromagnetic order in NiO Pt thin films. For rectangular elements patterned along the easy and hard magnetocrystalline anisotropy axes of our film, we observe different domain structures and we identify magnetoelastic interactions that are distinct for different domain configurations. We reproduce the experimental observations by modeling the magnetoelastic interactions, considering spontaneous strain induced by the domain configuration, as well as elastic strain due to the substrate and the shape of the patterns. This allows us to demonstrate and explain how the variation of the aspect ratio of rectangular elements can be used to control the antiferromagnetic ground state domain configuration. Shape dependent strain does not only need to be considered in the design of antiferromagnetic devices, but can potentially be used to tailor their properties, providing an additional handle to control antiferromagnet