This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A research team led by Professor Jung-Il Hong of the Department of Physics and Chemistry at DGIST has successfully used current pulses to alter the spin configuration within a ferrimagnetic material, lowering its "compensation temperature"—the temperature at which opposing magnetizations cancel each other out—by up to approximately 110 K. The research is published in the journal Advanced Functional Materials.
The team controlled the material's magnetic properties using only electrical signals, without changing the composition or thickness of the alloy. The technology could have applications in next-generation spintronic memory devices. Ferrimagnets are materials in which two types of magnetization coexist in opposite directions.
As temperature changes, the magnitudes of the two magnetizations also change, and at a certain temperature, they exactly cancel each other out. This temperature is known as the "compensation temperature." Near the compensation temperature, magnetization can be controlled rapidly and efficiently, making this property important for the development of high-speed, high-density memory devices. Traditionally, changing the compensation temperature has required modifying the alloy composition or thin-film thickness or applying additional processes such as heat treatment or ion implantation.
However, these approaches make it difficult to modify the magnetic properties at specific locations after a device has been fabricated. They may also alter the material's structure or composition during processing. The research team used "spin-orbit torque," which is generated by passing an electric current through a multilayer thin film composed of platinum (Pt), iridium manganese (IrMn₃) and cobalt-gadolinium (CoGd).
The current alters the spin configuration of IrMn₃, which in turn affects the spin state of the adjacent CoGd and changes its compensation temperature. In other words, the team altered the material's magnetic properties by electrically controlling only its internal spin configuration while leaving its composition unchanged. Experimental results showed that the compensation temperature of the Co₀.₅Gd₀.₅ thin film decreased by approximately 70 K, from around 350–360 K to approximately 280–290 K after the current was applied.
In the Co₀.₆₈Gd₀.₃₂ thin film, the compensation temperature likewise decreased from approximately 170–180 K to 60–70 K, representing a change of up to approximately 110 K. The research team confirmed that the magnetic properties could be precisely controlled simply by adjusting the intensity and duration of the current pulses. "This study demonstrates that the magnetic properties of a material can vary significantly depending not only on the types and spatial arrangement of its atoms but also on the configuration of its internal spins," said Professor Jung-Il Hong.
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