I think the iPhone 6 uses a Chinese Fluxgate chip. It also has barometric altitude, by the way
I read the phones use fluxgates. I have no idea how they got them so small and efficient. They also have Hall sensors but for things like sensing their cover. Hall sensors require a rather strong magnetic field. Incidentally, I’m actually in the business of selling all kinds of Hall sensors 
achimha wrote:
All electronic systems use fluxgates, just like the mobile phones.
What makes you think they use fluxgates?
Normally, these sensors use a magnetoresistive wheatstone bridge, like the classical Philips KMZ51
Typical phone compass chips still seem to use a magnetoresistive bridge, such as this ST one (see block diagram on page 8)
achimha wrote:
I read the phones use fluxgates
I read the iPhone 6 uses a 3-axis electronic compass IC with high sensitive Hall sensor technology and I2C interface (yum )
Best adapted to pedestrian city navigation use for cell phone and other portable appliance.
(AKM 8963)
