Nav: Home

When ultrafast laser pulse meets magnetic materials

February 17, 2017

Ultrafast non-equilibrium magnetization in correlated spin systems is extensively studied in recent years. At both fundamental and application levels, ultrafast laser pulse excitation and dynamics measurement provide an effective path to the fast optical detection, as well as for the control of the magnetic order. Measuring the time-resolved magneto-optical Kerr effect (TR-MOKE), ultrafast magnetic relaxation phenomenon such as ultrafast demagnetization and uniform precession are observed in magnetic media. The optically excited magnetization precession in magnetic media exhibits the temporal response of magnetization when the effective magnetic field is instantaneously changed by ultrafast laser pulse excitation and provides information about the spin dynamics microscopically.

Recently, extensive attentions have been paid to the BiFeO3 (BFO) and Sr-doped LaMnO3 heterostructure, for a series of novel physical properties that originate from the antiferromagnetic (AFM) and ferromagnetic (FM) exchange interaction across the heterointerface. In an article recently published in SCIENCE CHINA Physics, Mechanics & Astronomy, researchers at the Institute of Physics, Chinese Academy of Sciences, reported their investigation on the ultrafast laser-excited magnetization dynamics of ferromagnetic (FM) La0.67Sr0.33MnO3 (LSMO) thin films with epitaxial grown BiFeO3 (BFO) coating layers.

These researchers fabricated the BFO/LSMO heterostructure using the laser molecular beam epitaxy system. As they designed, 10-nm-thick LSMO thin films were deposited on (001) SrTiO3 (STO) single crystal substrates, and 3- or 20-nm-thick BFO films were coated onto the LSMO films. X-ray diffraction was carried out for structural characterization. With the ultrafast time-resolved magneto-optical Kerr effect (TR-MOKE) measurement system they built, the researchers measured the temporal response of the samples they prepared within the time scale of ~500 ps by pump-probe technique.

Two distinct types of oscillations were launched after the pump pulse excited the sample. The high-frequency oscillation at ~103 GHz was independent of the external magnetic field, which was ascribed to the coherent acoustic phonons generated in the STO substrates by the pump-pulse irradiation. The other oscillation mode occurred at a lower frequency (10-30 GHz), exhibiting a positive dependence on the external magnetic field. This relation confirmed the oscillation behavior to be the optically triggered magnetization precession, which has been extensively observed in magnetic media previously in ultrafast TR-MOKE measurements.

Intriguingly, by comparing the optically excited precession behavior of the different samples under the same external magnetic fields, the oscillation period of the precession appeared to be expanded for the BFO-coated LSMO films, and the sample coated with 20-nm-thick BFO exhibited a longer oscillation period than that coated with 3-nm-thick BFO. Fourier transforms show distinct shifts of the precession frequency peak position in each case for the same external magnetic field, thus confirmed the frequency modulation of the magnetization precession.

The researchers analyzed the effective magnetic field in the LSMO film and attributed the reduction of the precession frequency to the suppression of the anisotropy by BFO coating layers. Moreover, they suppose such behavior was induced by the exchange interaction across the BFO/LSMO interface.

"Investigating the optically excited magnetization precession in magnetic oxides may shed light on potential application in spintronics devices" wrote the researchers, "Our findings may provide an effective approach for controlling the spin behavior in magnetic oxide films through structural design".
This research was funded by the National Key Basic Research Program of China (Grant Nos. 2014CB921001, and 2013CB328706).

See the article:

Q. Wan, K. J. Jin, J. S. Wang, H. B. Yao, J. X. Gu, H. Z. Guo, X. L. Xu, and G. Z. Yang, Modulation of ultrafast laser-induced magnetization precession in BiFeO3-coated La0.67Sr0.33MnO3 thin films, Sci. China-Phys. Mech. Astron. 60, 047511 (2017)

Science China Press

Science China Press

Related Behavior Articles:

I won't have what he's having: The brain and socially motivated behavior
Monkeys devalue rewards when they anticipate that another monkey will get them instead.
Unlocking animal behavior through motion
Using physics to study different types of animal motion, such as burrowing worms or flying flocks, can reveal how animals behave in different settings.
AI to help monitor behavior
Algorithms based on artificial intelligence do better at supporting educational and clinical decision-making, according to a new study.
Increasing opportunities for sustainable behavior
To mitigate climate change and safeguard ecosystems, we need to make drastic changes in our consumption and transport behaviors.
Predicting a protein's behavior from its appearance
Researchers at EPFL have developed a new way to predict a protein's interactions with other proteins and biomolecules, and its biochemical activity, merely by observing its surface.
Spirituality affects the behavior of mortgagers
According to Olga Miroshnichenko, a Sc.D in Economics, and a Professor at the Department of Economics and Finance, Tyumen State University, morals affect the thinking of mortgage payers and help them avoid past due payments.
Asking if behavior can be changed on climate crisis
One of the more complex problems facing social psychologists today is whether any intervention can move people to change their behavior about climate change and protecting the environment for the sake of future generations.
Is Instagram behavior motivated by a desire to belong?
Does a desire to belong and perceived social support drive a person's frequency of Instagram use?
A 3D view of climatic behavior at the third pole
Research across several areas of the 'Third Pole' -- the high-mountain region centered on the Tibetan Plateau -- shows a seasonal cycle in how near-surface temperature changes with elevation.
Witnessing uncivil behavior
When people witness poor customer service, a manager's intervention can help reduce hostility toward the company or brand, according to WSU research.
More Behavior News and Behavior Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at