The Memsic AMR (anisotropic magnetoresistive) magnetometer is permalloy based ( alloy containing 80% nickel and 20% iron); the alloy's resistance decreases as the direction of magnetization rotates away from the direction in which current flows. It is low power and low cost. The TDK InvenSense magnetometer (only available in the 9-axis motion sensor) uses a 3-axis AKM Hall effect device.
Tablets/ Mobile Phones,
Link to Memsic