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Atomic Nuclei: Magnetic Resonance

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The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...

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Ferromagnetism

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Related Experiment Video

Updated: May 18, 2026

High-Temperature and High-Pressure In situ Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

High-Temperature and High-Pressure In situ Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

Published on: October 9, 2020

Fast magnetization switching by linear vertical microwave-assisted spin-transfer torque.

Congpu Mu¹, Weiwei Wang, Haiyan Xia

¹Institute of Applied Magnetics, Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, People's Republic of China.

Journal of Nanoscience and Nanotechnology

|October 6, 2012

Summary

Applying a vertical microwave magnetic field accelerates magnetization switching in elliptical magnetic spin valves. This method significantly reduces switching time and lowers critical current density for magnetic reversal.

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Area of Science:

Physics
Materials Science
Electrical Engineering

Background:

Spin-transfer torque (STT) is crucial for magnetic device operation.
Controlling magnetization switching speed is essential for high-performance spintronics.
Elliptical magnetic spin valves are key components in magnetic memory and logic devices.

Purpose of the Study:

To investigate the impact of a vertical microwave magnetic field on spin-transfer torque switching.
To determine how microwave field parameters influence magnetization switching time and critical current density.

Main Methods:

Micromagnetic simulations were employed.
A spin-transfer torque term was included in the simulations.
The effect of varying vertical microwave magnetic field amplitude and frequency was analyzed.

Main Results:

Vertical microwave magnetic field application accelerates magnetization switching.
Switching time decreases with increasing microwave field amplitude.
Minimum switching time (reduced from 9.44 to 2.4 ns) achieved at ferromagnetic resonance frequency.
Critical current density for magnetization reversal is significantly lowered.

Conclusions:

Vertical microwave magnetic fields offer an effective method to enhance STT switching in elliptical magnetic spin valves.
This technique can lead to faster magnetic devices with lower power consumption.
Optimizing microwave field parameters, particularly frequency, is key to maximizing performance gains.