Researchers from the Institute of Materials Science (ICMAB-CSIC), in collaboration with the ALBA Synchrotron, have designed new flexible and crystalline tapes made of an antiferromagnetic material. This innovation, which is published in the journal Applied Materials & Interfaces, allows the recording of magnetic information in a more secure and robust way, and could be integrated in flexible or wearable devices, such as credit or identification cards.

Antiferromagnetic materials offer a more robust alternative for storing information than ferromagnetic materials (the most widely used today to encode information, for example, on magnetic cards).

"Ferromagnets have been known for thousands of years and their behavior has been extensively studied. Antiferromagnetics, in which the magnetic moments of the atoms are spontaneously aligned antiparallel to the neighboring moments, can be used to store information, following certain protocols, providing greater security than ferromagnets", explains Ignasi Fina, ICMAB researcher and first author of the article.

The iron-rhodium alloy (FeRh) is one of the antiferromagnetic materials that can display these characteristics. Moreover, its antiferromagnetic arrangement is especially easy to manipulate thanks to the fact that it presents a transition from antiferromagnetic to ferromagnetic at a temperature near above room temperature.

Until now FeRh materials had not been integrated in conventional flexible devices (grown on polymeric substrates), because they need to show a good crystallinity (atoms arranged in a certain order) that allows stabilizing the antiferromagnetic ordering. The FeRh alloys are usually prepared on monocrystalline substrates, which makes them rigid and potentially fragile. 

A flexible material with a crystalline structure

"It is especially difficult to obtain a flexible material with a crystalline structure. Since the properties of the materials utterly depend on their structure, it is very important to obtain the material with a good crystallinity, which is what gives FeRh its unique properties for data recording," adds Ignasi Fina.

The study proofs the robustness of the magnetic properties of the material under bending, and the information storage in the tapes, which could be fabricated in meters-long tape, proving its affordable and feasible scale up.

"These flexible antiferromagnetic tapes have multiple applications in secure and robust magnetic recording, and could be integrated in real flexible or wearable devices, such as credit cards or identification cards, where security and robustness against electromagnetic radiation, for example from cell phones, is extremely important. Other possible niche applications arelikely to emerge when suitable prototypes become available" concludes the ICMAB researcher.

The research team will continue to work on this idea within the framework of an AGAUR/FEDER/GenCat project awarded in the LLAVOR 2019 call.

Article:

Flexible Antiferromagnetic FeRh Tapes as Memory Elements
Ignasi Fina, Nico Dix, Enric Menéndez, Anna Crespi, Michael Foerster, Lucia Aballe, Florencio Sánchez, Josep Fontcuberta.
ACS Appl. Mater. Interfaces 2020. Accepted: 9 March 2020. DOI: 10.1021/acsami.0c00704 

Links:

• Científicos del CSIC diseñan una nueva cinta flexible que permite almacenar información en dispositivos portátiles (CSIC, 27/03/2020)
• Científics del CSIC dissenyen una nova cinta flexible que permet emmagatzemar informació de forma més segura (CSIC Catalunya, 27/03/2020)
• Científics del CSIC dissenyen una alternativa més robusta per codificar informació digital (Europa Press, 27/03/2020)
• Diseñan una nueva cinta flexible que permite almacenar información en dispositivos portátiles (DICYT, 27/03/2020)

The study is related to these other previous publications:

1. Fina, J. Fontcuberta, Strain and voltage control of magnetic and electric properties of FeRh films. J. Phys. D: Appl. Phys.53, 023002 (2020).
2. Fina et al., Reversible and magnetically unassisted voltage-driven switching of magnetization in FeRh/PMN-PT. Appl. Phys. Lett.113, 152901 (2018).
3. Fina et al., Electric-Field-Adjustable Time-Dependent Magnetoelectric Response in Martensitic FeRh Alloy. ACS Applied Materials and Interfaces9, 15577-15582 (2017).
4. Fina, X. Marti, Electric Control of Antiferromagnets. IEEE Trans. Magn. 53, 2500107 (2017).
5. D. Clarkson et al., Hidden Magnetic States Emergent under Electric Field, in A Room Temperature Composite Magnetoelectric Multiferroic. Sci. Rep.7, 15460 (2017).
6. Saidl et al., Investigation of magneto-structural phase transition in FeRh by reflectivity and transmittance measurements in visible and near-infrared spectral region. New J. Phys.18, 083017 (2016).
7. Marti et al., Room-temperature antiferromagnetic memory resistor. Nat. Mater.13, 367-374 (2014).
8. Fina et al., Anisotropic magnetoresistance in an antiferromagnetic semiconductor. Nat. Commun.5, 4671 (2014).
9. Petti et al., Storing magnetic information in IrMn/MgO/Ta tunnel junctions via field-cooling. Appl. Phys. Lett.102, 192404 (2013).