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Materials

Tunnel magnetoresistance effect with a Cr-doped altermagnet

K. Tanaka, T. Nomoto, R. Arita

Featured August 3, 2026

Original Paper

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Simply

Scientists found that a special type of magnet called an altermagnet, made from Cr-doped RuO, can create a strong electrical resistance change when electrons tunnel through it, even though it has no overall magnetism.

In depth
The paper demonstrates that Cr-doped RuO$_{2}$ (110), an altermagnet, can generate a significant tunnel magnetoresistance (TMR) effect in magnetic tunnel junctions (MTJs). This is achieved by leveraging its unique momentum-dependent spin polarization, which, unlike conventional antiferromagnets, does not cancel out in the (110) crystal orientation, leading to enhanced TMR ratios up to ~300%.

Key Takeaways

  • 1
    Altermagnets like Cr-doped RuO can produce a finite tunnel magnetoresistance (TMR) effect by generating spin-polarized currents, despite lacking net magnetization.
  • 2
    The (110) crystal orientation of RuCrO is crucial, preventing spin polarization cancellation and leading to a significantly enhanced TMR ratio compared to (001) stacking.
  • 3
    The observed TMR effect is not solely explained by bulk spin polarization but is also strongly influenced by momentum-dependent spin splitting and interfacial magnetic structures within the tunnel junction.

Conceptual Flow

HIGH LEVEL
1
Methodology (The "Logic")

The scientists used powerful computer simulations to predict how a special magnet material would behave when electrons tunnel through it.

Material Design Ideas
Crystal Structure Rules
Simulate Electron Flow
Predicted Magnetism
Tunneling Behavior
2
Results (The "Impact")

They discovered that their new material design significantly boosts the tunneling resistance effect, especially when stacked in a specific way.

Standard Magnet Tunnel
New Material Tunnel
Compare Resistance Change
Much Higher Resistance Change