Who's the dope?

Doping the semiconductor material gallium arsenide, GaAs, with manganese leads to a so-called dilute magnetic semiconductor. This new material could be used to shrink the size of the read heads used in hard drives and so boost capacity significantly without increasing the size of the disk, according to UK scientists. David Williams, the head of the Hitachi Laboratory at Cambridge University, and his colleagues discovered that manganese-doped GaAs exhibits tunneling anisotropic magnetoresistance (TAMR). Working with Bryan Gallagher at Nottingham University they built a mock-up read head just a few tens of nanometers across. Despite the small size of the device, the team was able to produce a large response. The researchers admit it is early days and there is a lot more work to be done in understanding the behaviour of the material.