The paper

1. Goal: Find cobalt molecules that keep their magnetic “north” and “south” better than today’s best single-molecule magnets.

2. What they did

   • Built a big digital library of 15,000-plus virtual cobalt complexes.

   • Optimized each one with quantum chemistry to measure its magnetic “lock-in” strength (the axial anisotropy D).

3. Big discovery: You don’t need fragile two-coordinate cobalt.
   A simple rule works:

   Put two strong, straight-line (“axial”) ligands very close to cobalt and keep all other bonds weaker or farther away.
   This “pseudo-linear” setup lets the cobalt keep a big orbital moment → huge magnetic anisotropy.

4. Numbers that matter

   • Nearly 200 new designs beat |D| > 100 cm⁻¹, many in 4–5 coordination.

   • One record hit reached |D| ≈ 250 cm⁻¹—better than any cobalt magnet reported so far.

5. Why it matters

   • Chemists now have a clear design recipe that is easier to synthesize and more stable than ultra-low-coordination compounds.

   • All data are released as the COMPASS database, so anyone can train ML models or pick promising targets for the lab.

Bottom line: give cobalt a straight, two-bond “spine,” relax the side bonds, and you unlock record-size magnetic stickiness—opening new paths to strong molecular and bulk magnets.

Translating it to Fe

2. Why iron is trickier than cobalt

• Iron’s built-in “magnet locking” power (spin-orbit coupling) is only about one-third of cobalt’s.

• So we need to help iron by:

  1. Keeping the same two-bond line, and

  2. Adding things that boost the effect—heavier neighbor atoms, stretched lattices, or extra strain.

3. Simple design rules for iron magnets

1. Short north-south bonds: Put atoms like N, B, Sb, or Ni directly above and below each iron atom.

2. Loose east-west bonds: Make the side bonds longer or weaker so they don’t cancel the effect.

3. Heavy helpers: Surround iron with a few heavier atoms (Ni, Sb, W, Pt) to amplify the locking power.

4. Built-in stretch: Use crystal structures that are naturally longer in one direction (tetragonal) or apply strain during processing.

4. Real-world crystal families that already follow these rules

Bottom line:

Treat each iron atom like a tiny bar magnet: clamp it firmly from the top and bottom, leave its sides free, and give it a heavier buddy or a bit of stretch. Do that, and cheap, earth-abundant iron can inch closer to the performance of today’s rare-earth super-magnets.