Imagine touching a non-magnetic material and everywhere you touched became magnetic and remained so forever. Such a magnetic Midas touch has become a reality thanks to PARADIM. All that is needed to turn on the magnetism is a brief pulse of heat. A local temperature change of 50-100°C is sufficient to switch the material into a ferromagnetic state, and it remains in that state after cooling back to room temperature. The human finger isn’t quite hot enough to accomplish this, but a laser beam is. With a laser, PARADIM users wrote “Cornell.” Further, the pattern can be erased by cooling it below room temperature.
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Figure: Cartoon of the writing process by local heating with a focused laser beam (selected as journal inside cover). Magnetization measured at room temperature of a sample before and after writing and after full erasure of the letters by cooling. Color represents the magnetization strength |
This ability to controllably write, erase, and rewrite magnetic patterns in an otherwise non-magnetic material is the basis for magnetic data storage, logic devices, and other applications. The material allowing this is a precise alloy of iron and rhodium (Fe0.52Rh0.48) grown as a thin film in PARADIM.
The creation of artificial patterns provides an exciting platform to study magnetic interactions in any configuration and to explore the functionality of novel magnetic devices.
Antonio B. Mei et al., Adv. Mater. 32 (2020) 2001080.
Technical details: The ability to controllably create and erase patterns of magnetic structures within an otherwise nonmagnetic material is the foundation of magnetic memory and logic devices, allows the creation of artificial spin‐ice lattices, and enables the study of magnon propagation. Here, a novel approach for magnetic patterning that allows repeated creation and erasure of arbitrary shapes of ferromagnetic structures in thin films is reported. This is enabled by epitaxial Fe0.52Rh0.48 thin films designed so that both ferromagnetic and antiferromagnetic phases are bistable at room temperature.
Intermetallic Fe1−xRhx exhibits a hysteretic antiferromagnetic/ferromagnetic transformation. The thin films are grown epitaxially on single‐crystalline (001)‐oriented MgO substrates using molecular‐beam epitaxy. In this study, PARADIM users engineered the width of the thermal hysteresis to be sufficiently narrow to enable efficient controllability, but also wide enough to robustly withstand thermal perturbations. Moderate heating by a focused pulsed laser is used to locally drive antiferromagnetic regions controllably to the ferromagnetic phase, demonstrating the patterning of arbitrary magnetic features on sub‐micrometer length scales and ≈100 ps time scales. If desired, the written information can then be erased by cooling below room temperature and the material repeatedly re‐patterned.
These findings present opportunities for writing and erasing high‐fidelity magnetically active nanostructures that are of interest for magnonic crystals [1], artificial spin‐ice lattices [2], and ultrafast magnetic memory [3-6] and logic devices [7].
Full journal citation: Antonio B. Mei, Isaiah Gray, Yongjian Tang, Jürgen Schubert, Don Werder, Jason Bartell, Daniel C. Ralph, Gregory D. Fuchs, and Darrell G. Schlom, “Local Photothermal Control of Phase Transitions for On-Demand Room-Temperature Rewritable Magnetic Patterning,” Adv. Mater. 32 (2020) 2001080.
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