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Title: Frequency driven inversion of tunnel magnetoimpedance and observation of positive tunnel magnetocapacitance in magnetic tunnel junctions

Abstract

The relevance for modern computation of non-volatile high-frequency memories makes ac-transport measurements of magnetic tunnel junctions (MTJs) crucial for exploring this regime. Here, we demonstrate a frequency-mediated effect in which the tunnel magnetoimpedance reverses its sign in a classical Co/Al{sub 2}O{sub 3}/NiFe MTJ, whereas we only observe a gradual decrease in the tunnel magnetophase. Such effects are explained by the capacitive coupling of a parallel resistor and capacitor in the equivalent circuit model of the MTJ. Furthermore, we report a positive tunnel magnetocapacitance effect, suggesting the presence of a spin-capacitance at the two ferromagnet/tunnel-barrier interfaces. Our results are important for understanding spin transport phenomena at the high frequency regime in which the spin-polarized charge accumulation due to spin-dependent penetration depth at the two interfaces plays a crucial role.

Authors:
; ; ;  [1];  [1];  [2];  [1];  [3]; ;  [1];  [4]
  1. CIC nanoGUNE, 20018 Donostia-San Sebastian (Spain)
  2. (Germany)
  3. (China)
  4. (Spain)
Publication Date:
OSTI Identifier:
22594395
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALUMINIUM OXIDES; BUILDUP; CALCULATION METHODS; CAPACITANCE; CAPACITORS; COUPLING; EQUIVALENT CIRCUITS; INTERFACES; MAGNETIC TUNNEL JUNCTIONS; PENETRATION DEPTH; RESISTORS; SPIN; SPIN ORIENTATION; VOLATILITY

Citation Formats

Parui, Subir, E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu, Ribeiro, Mário, Atxabal, Ainhoa, Llopis, Roger, Bedoya-Pinto, Amilcar, Max Planck Institute of Microstructure Physics, D-06120 Halle, Sun, Xiangnan, National Center for Nanoscience and Technology, 100190 Beijing, Casanova, Fèlix, Hueso, Luis E., E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu, and IKERBASQUE, Basque Foundation for Science, 48011 Bilbao. Frequency driven inversion of tunnel magnetoimpedance and observation of positive tunnel magnetocapacitance in magnetic tunnel junctions. United States: N. p., 2016. Web. doi:10.1063/1.4960202.
Parui, Subir, E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu, Ribeiro, Mário, Atxabal, Ainhoa, Llopis, Roger, Bedoya-Pinto, Amilcar, Max Planck Institute of Microstructure Physics, D-06120 Halle, Sun, Xiangnan, National Center for Nanoscience and Technology, 100190 Beijing, Casanova, Fèlix, Hueso, Luis E., E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu, & IKERBASQUE, Basque Foundation for Science, 48011 Bilbao. Frequency driven inversion of tunnel magnetoimpedance and observation of positive tunnel magnetocapacitance in magnetic tunnel junctions. United States. doi:10.1063/1.4960202.
Parui, Subir, E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu, Ribeiro, Mário, Atxabal, Ainhoa, Llopis, Roger, Bedoya-Pinto, Amilcar, Max Planck Institute of Microstructure Physics, D-06120 Halle, Sun, Xiangnan, National Center for Nanoscience and Technology, 100190 Beijing, Casanova, Fèlix, Hueso, Luis E., E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu, and IKERBASQUE, Basque Foundation for Science, 48011 Bilbao. 2016. "Frequency driven inversion of tunnel magnetoimpedance and observation of positive tunnel magnetocapacitance in magnetic tunnel junctions". United States. doi:10.1063/1.4960202.
@article{osti_22594395,
title = {Frequency driven inversion of tunnel magnetoimpedance and observation of positive tunnel magnetocapacitance in magnetic tunnel junctions},
author = {Parui, Subir, E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu and Ribeiro, Mário and Atxabal, Ainhoa and Llopis, Roger and Bedoya-Pinto, Amilcar and Max Planck Institute of Microstructure Physics, D-06120 Halle and Sun, Xiangnan and National Center for Nanoscience and Technology, 100190 Beijing and Casanova, Fèlix and Hueso, Luis E., E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu and IKERBASQUE, Basque Foundation for Science, 48011 Bilbao},
abstractNote = {The relevance for modern computation of non-volatile high-frequency memories makes ac-transport measurements of magnetic tunnel junctions (MTJs) crucial for exploring this regime. Here, we demonstrate a frequency-mediated effect in which the tunnel magnetoimpedance reverses its sign in a classical Co/Al{sub 2}O{sub 3}/NiFe MTJ, whereas we only observe a gradual decrease in the tunnel magnetophase. Such effects are explained by the capacitive coupling of a parallel resistor and capacitor in the equivalent circuit model of the MTJ. Furthermore, we report a positive tunnel magnetocapacitance effect, suggesting the presence of a spin-capacitance at the two ferromagnet/tunnel-barrier interfaces. Our results are important for understanding spin transport phenomena at the high frequency regime in which the spin-polarized charge accumulation due to spin-dependent penetration depth at the two interfaces plays a crucial role.},
doi = {10.1063/1.4960202},
journal = {Applied Physics Letters},
number = 5,
volume = 109,
place = {United States},
year = 2016,
month = 8
}
  • The frequency dependence of tunneling magnetocapacitance (TMC) in magnetic tunnel junctions (MTJs) is investigated theoretically and experimentally. According to the calculation based on Debye-Fröhlich model combined with Julliere formula, the TMC ratio strongly depends on the frequency and it has the maximum peak at a specific frequency. The calculated frequency dependence of TMC is in good agreement with the experimental results obtained in MgO-based MTJs with a tunneling magnetoresistance (TMR) ratio of 108%, which exhibit a large TMC ratio of 155% at room temperature. This calculation also predicts that the TMC ratio can be as large as about 1000% formore » a spin polarization of 87%, while the TMR ratio is 623% for the same spin polarization. These theoretical and experimental findings provide a deeper understanding on AC spin-dependent transport in the MTJs and will open up wider opportunities for device applications, such as highly sensitive magnetic sensors and impedance-tunable devices.« less
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  • Magnetic 1/f noise is compared in magnetic tunnel junctions with electron-beam evaporated and sputtered MgO tunnel barriers in the annealing temperature range 350 - 425 Degree-Sign C. The variation of the magnetic noise parameter ({alpha}{sub mag}) of the reference layer with annealing temperature mainly reflects the variation of the pinning effect of the exchange-bias layer. A reduction in {alpha}{sub mag} with bias is associated with the bias dependence of the tunneling magnetoresistance. The related magnetic losses are parameterized by a phase lag {epsilon}, which is nearly independent of bias especially below 100 mV. The similar changes in magnetic noise withmore » annealing temperature and barrier thickness for two types of MgO magnetic tunnel junctions indicate that the barrier layer quality does not affect the magnetic losses in the reference layer.« less
  • Stress-annealed nanocrystalline FeCuNbSiB ribbons show correlation between induced magnetic anisotropy and magnetoimpedance. Two types of crystallization process were used in order to induce a transverse magnetic anisotropy: the first one was performed submitting the original amorphous samples to an applied tensile stress of {sigma} = 150 MPa. In the second one, samples are nanocrystallized in a first stage and submitted to stress annealing at {sigma} = 290 MPa afterwards. The maximum of the magnetoimpedance can be obtained for dc fields larger than the anisotropy field of the sample of close to the irreversibility field. This behavior can be explained basedmore » in the simultaneous switching of two different magnetization processes taking place in the samples with high transverse magnetic anisotropy.« less