ROOM-TEMPERATURE MAGNETORESISTANCE IN AN OXIDE MATERIAL WITH AN ORDERED DOUBLE-PEROVSKITE STRUCTURE

Colossal magnetoresistance-a huge decrease in resistance in response t o a magnetic field-has recently been observed in manganese oxides with perovskite structure. This effect is attracting considerable interest from both fundamental and practical points of view(1). In the context of using this effect in practical devices, a noteworthy feature of th ese materials is the high degree of spin polarization of the charge ca rriers, caused by the half-metallic nature of these materials(20,21); this in principle allows spin-dependent carrier scattering processes, and hence the resistance, to be strongly influenced by low magnetic fi elds. This type of field control has been demonstrated for charge-carr ier scattering at tunnelling junctions(2,3) and at crystal-twin or cer amic grain boundaries(4,5), although the operating temperature of such structures is still too low (less than or equal to 150K) for most app lications. Here we report a material-Sr2FeMoO6, an ordered double pero vskite(6)-exhibiting intrinsic tunnelling-type magnetoresistance at ro om temperature. We explain the origin of this behaviour with electroni c-structure calculations that indicate the material to be half-metalli c. Our results show promise for the development of ordered perovskite magnetoresistive devices that are operable at room temperature.