Query the IMU’s magnetometer and return the magnetic field in uT (micro Tesla).
IMU.readMagneticField(x,y,z)
1 on success, 0 on failure.
float x, y, z;
if (IMU.magneticFieldAvailable()) {
IMU.readMagneticField(x, y, z);
Serial.print(x);
Serial.print('\t');
Serial.print(y);
Serial.print('\t');
Serial.println(z);
}