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Inverse-Voltage Controlled Magnetic Anisotropy effect: a new phenomenon for generation of charge current from oscillating magnetization

Name: Ambika Shukla

Department: Electrical Engineering

Program: Ph. D.

Name of supervisor: Prof. Ashwin Tulapurkar

When we think beyond Moore's law we find Spintronic technology is the most promising one and have potential to dominate entire consumer electronics market. Contemporary CMOS devices works on electron charge whereas spintronic devices exploit quantum mechanical property of electrons called spin. This technology helps in getting devices faster and consume ultra-low power. These two advantageous over existing technology makes it most prominent candidate for Space and Defense application where you need more complexity in chips with less floor area. This technology also attracts scientific brains around the globe to unearth new physics and develop new devices which may fill gap between existing and next generation electronics. If you look at the current scenario then Everspin technology has already launched Spin transfer torque based memory devices and is commercially available for end users.

In this new study we have shown generation of charge current from oscillating magnetization.

We design a project which focuses mainly on ultra-low power consumption and we exploited a fact that oscillating magnetization induces charge current in a circuit via the Faraday's law of elec- tromagnetic induction. New physical phenomena by which oscillating magnetization can produce charge current have gained considerable interest recently. For example, moving magnetization tex-tures such as domain walls, generate charge current through the spin-motive force. Here we have shown that an entirely different effect, which couples the magnetization and electric field at the interface between an ultrathin metallic ferromagnet and dielectric, can convert magnetic energy into electrical energy. This phenomenon is Onsager reciprocal of the voltage controlled magnetic anisotropy effect.

Stack of thin films were deposited at AIST-Ibaraki Japan we then fabricated tunnel junctions of 3_m by 80_m dimension with top and bottom contacts for Inverse-VCMA devices at IIT Bombay Nano-fabriaction (IITBNF)facility using standard CMOS compatible fabrication technique. We then characterizes these devices in our Spintronics lab using \Arihant" the Magneto-Electric probe station with 360 deg. out of plane rotating stage and is well equipped with both DC and RF probes.S-parameters of device were then measured using vector network analyzer (VNA) (R&S model no. ZNB-20) at a fixed frequency while sweeping external magnetic field from +/-2000(Oe) Oe.We used high-frequency GS probes from GGB Industries.

Conclusion and Applications

In conclusion, our results provide a new avenue to generate charge current from the magnetization oscillation. This can offer an alternative route to convert magnetic energy into electrical energy and a new probe for the magnetization dynamics of nanomagnets. We also believe that the findings will pave a new path for ultra-low power digital data storage devices, in micro-chips for space application where power consumption is major challenge and will be very useful in designing self-powered Neuromorphic computing devices.


We would like to acknowledge the support of Centre of Excellence in Nanoelectronics (CEN) at Indian Institute of Technology Bombay Nanofabrication facility (IITBNF) and Industrial Research and Consultancy Center (IRCC), IIT Bombay, Mumbai, India for financial support. We acknowledge the support of Department of Science and Technology (DST), Government of India throughproject no. SR/NM/NS-1112/2016 and Science and Engineering Research Board (SERB) through project no. EMR/2016/007131.