A near-monochrome collage of seven laboratory photographs cut into diagonal panels: a cryostat and vacuum chamber trailing cabling and steel flanges; an optical table with posts, a glowing lamp and a circuit board; a bright ring of light seen through a dark chamber viewport; a chamber interior with a finned copper disc, translation stages and stepper motors; a rack of long cryostat probe inserts with stacked baffles; a vacuum chamber wrapped in aluminium foil with pneumatic valves; and a chamber with a brilliant glowing plume beneath a circular electrode.

Methods

Each research page is written around the question that project asked. This page is the layer underneath all of them: what has to be built, deposited, patterned, measured and logged before any of those questions can be answered, and which project each piece was built for.

Making the devices

Exfoliation and dry-transfer stacking. Bulk crystals, supplied by growth collaborators, are mechanically or polymer-exfoliated to thin flakes and stacked into heterostructures by polymer dry transfer inside a glove box, since every antiferromagnet used here degrades in air. I co-built and optimised the polymer dry-transfer route the subgroup uses, and co-implemented the automated transfer setup for twisted stacks. Used in all three published exchange-bias systems and in the magnon spin valve.

Lithography. Optical lithography on a mask aligner and a laser writer for contact-pad level, electron-beam lithography for the device geometry. The optical lithography recipes for these stacks were optimised by me. Resist is removed by oxygen-plasma ashing.

Etch and deposition. Ion-beam etching for pattern definition. Sputter deposition of platinum and of gold contacts, run inside the glove box where the stack underneath is air-sensitive. Molecular-beam epitaxy sessions for platinum on CrPS4 were run alongside the group's MBE operator rather than by me alone.

Interface routes. For the Pt/CrPS4 system, the interface was characterised along two competing routes, platinum deposited onto an exfoliated flake and a flake transferred onto pre-deposited platinum, each across several deposition and transfer conditions. That comparison is what fixed the recipe the magnon spin-valve devices are still built to.

Checking them

In-house SEM and EDX. Every fabricated device gets a structural and compositional check before it enters a measurement campaign. I established this as the standard handover step because external microscopy shifts were a recurring bottleneck.

Structural and chemical characterisation. Atomic force microscopy for layer thickness and surface quality, Raman spectroscopy on individual crystals and on the finished stack.

External metrology campaigns. FIB-SEM, STEM, STEM-EELS for the interfaces, and Lorentz STEM and off-axis electron holography for the magnetic structure, all in collaboration with Forschungszentrum Jülich. My part was the planning side: what to cut, where, which tool answers which question, and how to fit that into the instrument availability the partner had. The holographic induction map on the orthogonal exchange-bias page came out of one of these campaigns.

Magnetometry. SQUID magnetometry for bulk hysteresis and the exchange-bias shift, NV-centre magnetometry for stray-field imaging of individual domains.

Measuring them

Cryogenic transport. Magnetoresistance and Hall measurements at liquid-helium temperature, on a 12 T superconducting magnet and on a vector cryostat. The spin-Hall-magnetoresistance workflow on the 12 T magnet was brought into routine use by me during the visiting-researcher year, together with the Python routine that separates the SMR contribution from the competing transport effects in the same signal.

High-impedance chain. Tunnel junctions with an insulating barrier sit at resistances where the wiring, not the device, sets what can be measured. Cable qualification by time-domain reflectometry on a vector network analyser, single-point grounding and end-to-end shielding are what make a bias sweep on those devices trustworthy. Built for the CrSBr magnetoresistance study and now the subgroup standard for high-resistance van der Waals junctions.

Recording it

Instrument control. CryoSoft drives the cryogenic benches: config-driven instrument swaps, automated sweeps that run 20 to 30 hours unattended with safety limits enforced in software, and a full instrument snapshot written alongside every data point.

Data and metadata. One HDF5 file per run, carrying the run's own metadata and a per-sweep-point snapshot of every instrument in the chain, so a measurement artefact can be traced back to the state of the setup that produced it.

Analysis. One self-contained Python repository per published paper, installable in a single command, in which every figure regenerates from raw data. The three exchange-bias repositories are linked from their research pages.