Antiferromagnetic materials (AFMs) provide a pathway to overcome the limitations of ferromagnet-based spintronics, enabling fast and high density memory devices, as well as terahertz detectors and sources. This has fueled intensive research on the electrical manipulation of metallic AFMs using interfacial spin-orbit torque (SOT) from a heavy metal (HM) layer [1-4]. However, the threshold current density in HM/AFM bilayers is typically large, thus creating non-magnetic contributions to resistive switching signals, complicating their interpretation. Here, we present a new device structure and measurement protocol based on differential voltage measurements, allowing in situ reference measurements and to systematically separate the switching signals originating in the AFM and HM layers of a HM/AFM heterostructure [5]. The proposed device consists of a double-cross HM structure with six terminals, where the AFM, patterned in a micropillar shape, is placed on one of the two crosses. We successfully use this method in devices formed by Pt and the non-collinear AFM IrMn3. The results provide clear evidence of electrical switching of the AFM order parameter in the IrMn3 pillar by SOT in the range of writing current densities from 36 to 50 MA/cm2 with no appreciable switching signal from the Pt layer. We discuss the role of different switching configurations (180° and 90° writing currents), as well as the role of thermal activation on the switching characteristics. Control experiments in Pt-only double-cross samples without an AFM pillar reveal HM-dominated switching at higher current densities ~60 MA/cm2. We discuss active readout of the switching signals using a differential amplifier, with large peak-to-peak output voltage ~100 mV. The structure allows for reliable electrical measurement of resistive signatures of AFM switching induced by SOT, which will be important not only for the fundamental understanding of current-induced AFM domain dynamics, but also as an electrical readout method for practical applications in memory and computing devices.

![](https://assets.underline.io/uploads/markdown_image/1/image/9f7b7e5713bbb79e6a1b7f3436e814c5.jpg)

Fig. 1. Design of double-cross device for differential voltage measurements and the measured differential voltage for the 180° switching configuration with 20 mA write pulses.

Observation of current-induced switching in non-collinear antiferromagnetic IrMn3 by differential voltage measurements

Abstract Body: Continued advancement in renewable energy science relies on the discovery of new organic photovoltaic materials with high quantum efficiency, stability, and reliability. Recently, non-fullerene acceptors (NFAs) have shown tremendous improvements in power conversion efficiency, ~18 %, that is attributed to wide spectral absorption, efficient exciton dissociation, and strong π-π interactions leading to excellent charge transport and collection. However, there still are significant losses in all steps of photoconversion that need to be understood and minimized. Conventional ultrafast spectroscopy methods have been effective in understanding intrinsic losses involving excited state relaxation and charge transfer in bulk heterojunctions. However, extrinsic losses are known to dominate in bulk heterojunctions due to non-ideal band energetics, disordered morphology and packing, and poor interfaces and contacts. Electric charge-based spectroscopies, such as impedance, transient, and noise spectroscopy, provide a direct probe to these relatively slow processes. Non-invasive in-situ characterization reveals performance-limiting dynamical processes in fully fabricated devices in operational conditions. In this talk, impedance spectroscopy methods will be discussed in the context of NFA-based organic solar cells. Emerging NFA-polymer systems, including perylenediimide-, indacenodithienothiophene-, and Y6-based NFAs, will be used to demonstrate the effectiveness of impedance spectroscopy methods in this context.1-5 In particular, the beneficial role of annealing in ITIC- and Y6-based blends will be elucidated through reduced bimolecular recombination that is further correlated with improved morphology and packing motifs. Integration of impedance parameters with intensity-dependent photocurrent enables more realistic device models that can distinguish the competing effects of end-group functionalization in NFA molecules. This method will be shown to reveal different routes of performance improvement via π-extension and fluorination of NFAs. In this manner, the new understanding gained in these systems is likely to pave the way for further optimization of high performance and stable solar cells. References: 1 Journal of the American Chemical Society 142, 14532 (2020). 2 Adv. Eng. Mater. 10, 2000635 (2020). 3 ACS Eng. Lett. 5, 1780 (2020). 4 ACS Appl. Mater. Inter. 11, 14166 (2019). 5 Adv. Funct. Mater. 27, 1703805 (2017).

Impedance Spectroscopy for Emerging Non-Fullerene Acceptor Based Organic Solar Cells

**Session chair:** Romain Lebrun, Unité Mixte de Physique CNRS/Thales



GOP - Antiferromagnetic Spintronics II

technical paper

The 15th Joint MMM-INTERMAG Conference (2022 Joint) is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a plenary session, and an evening session, with about 1500 presentations overall. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

The 2022 Joint Conference will offer both in-person and prerecorded on-demand content.

For tickets to the event, please register at the following link: https://magnetism.org/register

Please register for the Joint MMM-Intermag conference to join the event.

2022 Joint MMM-INTERMAG

This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

Z: Solar Cell Materials and Devices

The Electronic Materials Conference (EMC) is the premier annual forum on the preparation, characterization and use of electronic materials. This year’s event will feature a plenary session, topical sessions, a poster session and more.

EMC is coordinated with the Device Research Conference (DRC), which will be held during the same week, from June 20-23. This recognizes the strong interaction between device and electronic materials research and provides fruitful exchange of information between attendees of both Conferences.

![](https://assets.underline.io/uploads/markdown_image/1/image/eb26c24a18d5d1030616afa4f993cf89.png)
	
<a href="https://www.mrs.org/docs/default-source/meetings-events/mrs-conference-services/2021/emc-2021/2021-emc-program-at-a-glance-6-16-21.pdf?sfvrsn=e39f950c_4">Latest Program-at-a-Glance</a>

<a href="https://drive.google.com/file/d/1eiS1ao4p83VNy8xgHs3Rls7gTQjx7Rc4/view?usp=sharing">Full Program with Abstracts</a>

Vinod K. Sangwan

2

13

2

Presentations

Observation of current-induced switching in non-collinear antiferromagnetic IrMn3 by differential voltage measurements

Impedance Spectroscopy for Emerging Non-Fullerene Acceptor Based Organic Solar Cells

Stay up to date with the latest Underline news!

PRESENTATIONS

CONFERENCES

COMPANY

RESOURCES