Thank you for your inquiry.
TurtleBot3 is widely used platform for a prototyping and researching purpose.
Many features based on ROS and other libraries are available and being tested by worldwide engineers, and you can see how these are applied on TurtleBot3.
For example, TurtleBot3 AutoRace use Raspberry Camera to detect lanes and various signs or QR markers.
Home Service Challenge that create a map and read various QR marker from different locations to deliver objects might be the one you want to see what can be done with TurtleBot3
If you are planning to use a magnetic field, you should attach a sensor that can read the magnetic field.
I didn't fully understand what you mean by matching the value of Magnetic field and Augmented Reality, but reading magnetic field and displaying the heading of the robot seems possible with a proper sensor.