Abstract
Voltage driven magnetic switching (VDMS) in multiferroic heterostructure is highly demanded for next generation energy efficient high-density memory (e.g. magnetoelectric random access memory) and spintronic devices. For practical applications in large scale integrated device, it is imperative to understand the VDMS behaviors in nanometer scale. In this work, we have investigated the effects of geometric and anisotropy parameters on 180° VDMS behaviors in a model multiferroic heterostructure system consisting of Co nano-ellipse on BiFeO3 films by using micromagnetic simulation. It was revealed that the switching behaviors can be greatly affected by geometric factors, whereby dimension shrinkage and rising aspect ratio of Co nano-ellipse can apparently increase the critical exchange coupling field (hDMcri-field) needed for triggering the VDMS, greatly reducing the watchability of VDMS. To improve the watchability, an external static perpendicular magnetoanisotropy (Kp) can be introduced to reduce the hDMcri-field, whereas too large Kp tends to reorientate the magnetization towards out-of-plane orientation. Moreover, a strategy was also proposed to assist the VDMS by applying an anisotropy pulse, which is able to reduce the hDMcri-field and expand the switching window (e.g. wider range of aspect ratio and overall dimension size) for both in-plane and out-of-plane VDMS. These results may provide some guides for further experimental modulation of VDMS for device applications.
Highlights
In the past decade, voltage driven magnetic switching (VDMS) has been intensively investigated due to its application potentials in energy efficient spintronic and memory devices.1–9 In the modern magnetic random access memory (MRAM) technology, writing a data bit is usually realized via magnetic states witching driven by external magnetic field or spin-torque effect, which requires large electric current and is energy inefficient.10,11 This problem can be well addressed if utilizing insulating multiferroic heterostructure that allows switching of magnetization by voltage pulses rather than large current, dramatically reducing power consuming as well as Joule heat.To exploit Voltage driven magnetic switching (VDMS) for device application, it is a prerequisite to achieve a robust yet repeatable voltage driven 180○ magnetization reversal in nanometered multiferroic heterostructure at room temperature
We have investigated the effects of geometric and anisotropy parameters on 180○ VDMS behaviors in a model multiferroic heterostructure system consisting of Co nano-ellipse on BiFeO3 films by using micromagnetic simulation
It is noted that for a typical exchange coupling based multiferroic heterostructure, e.g. Co/BFO, the intrinsic coupling field hDM is rather small (∼100 Oe),34,35,38–40 the VDMS can only occur at very narrow aspect ratio range (1 to 1.15), as marked in the shallow region
Summary
Voltage driven magnetic switching (VDMS) has been intensively investigated due to its application potentials in energy efficient spintronic and memory devices. In the modern magnetic random access memory (MRAM) technology, writing a data bit is usually realized via magnetic states witching driven by external magnetic field or spin-torque effect, which requires large electric current and is energy inefficient. This problem can be well addressed if utilizing insulating multiferroic heterostructure that allows switching of magnetization by voltage pulses rather than large current, dramatically reducing power consuming as well as Joule heat. In the modern magnetic random access memory (MRAM) technology, writing a data bit is usually realized via magnetic states witching driven by external magnetic field or spin-torque effect, which requires large electric current and is energy inefficient.10,11 This problem can be well addressed if utilizing insulating multiferroic heterostructure that allows switching of magnetization by voltage pulses rather than large current, dramatically reducing power consuming as well as Joule heat. It was reported that pure voltage driven magnetic switching via interfacial exchange coupling, which has proven to be able to trigger both 90○ and 180○ net magnetic switching induced by electric voltage.36–39 These progresses have pushed forward the realization of generation VDMS devices. Our results may provide some insights into the VDMS behaviors in low dimension system, and suggest new routes to develop nanoscale heterostructure for high density VDMS integrated devices
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