Layered chromium triiodide crystals exhibit massive tunneling magnetoresistance, reaching an extraordinary 10,000% magnitude.
In short: Tunneling magnetoresistance is a quantum phenomenon where electrical resistance shifts based on the magnetic alignment of a junction. While traditional devices use complex thin-film stacks, researchers have discovered that exfoliated crystals of the semiconductor chromium triiodide naturally produce massive resistance changes, revealing a deep, inherent coupling between magnetism and electronic transport.
Tunneling magnetoresistance (TMR) is a quantum-mechanical effect occurring in magnetic tunnel junctions, where electrons traverse an insulating barrier between two ferromagnetic layers. In classical physics, this process is forbidden, but in the realm of spintronics, it allows for the switching of electrical resistance between high and low states. Traditionally, these junctions are engineered using thin-film technology, such as magnetron sputtering, to create precise interfaces between ferromagnets and insulators like magnesium oxide.
Recent investigations into van der Waals compounds have shifted the focus toward materials like chromium triiodide (CrI3). Unlike conventional semiconductors that require magnetic dopants to exhibit magnetism, CrI3 possesses spontaneous ferromagnetism. Experiments on nano-fabricated devices using exfoliated CrI3 crystals have demonstrated that this material exhibits a very large TMR, reaching up to 10,000%. This effect originates from abrupt transitions between different magnetic states within the crystal, providing direct evidence of strong coupling between the material's magnetic properties and its transport behavior.
The behavior of CrI3 devices is distinct from standard semiconductors. While field-effect transistors based on CrI3 show resistance that becomes unmeasurably high below 100 K, vertical junctions allow for transport measurements at much lower temperatures. Data from devices with a thickness of approximately 7 nm, or 10 monolayers, reveal nonlinear current-voltage curves that remain temperature-independent below 20 K. This stability suggests that vertical transport perpendicular to the layers is a powerful tool for probing magnetic phenomena in atomically thin materials, potentially offering a new frontier for spintronic applications beyond the current reliance on complex multilayer stacks.
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Sources
- Summary by Intellect · source: Very large tunneling magnetoresistance in layered magnetic semiconductor CrI3 - Nature Communications
- Also: Tunnel magnetoresistance
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