Realistic Magnetometer Specifications
If the magnetic sensor will saturate they provide reset straps on magnetometers for degaussing. If those aren't working then your exceeding the maximum filed strength of the HMC5883L magnetometer, which is: 8 gauss = 0.0008 Tesla.

The HMC1001 may be more of what your looking for which is good for 10000 gauss = 1 Telsa , but it requires analog electronics (you should be able to find an eval board). By 1 Tesla, I mean if you exceed 1 Tesla, you will ruin the sensor. The acutal range of the sensor is much lower than that, but depends on the gain of the analog electronics.

If you need something beyond that, your probably not going to find it in a magnetometer, because its well outside the range people normally want to sense in.  

Either place your magnetometer further away from the electromagnet and use the set/reset straps to degauss it (you have possibly ruined the ones you have).  

Look at hall effect sensors, they are better at this kind of thing and some work above 10 Tesla.

I believe that most of honeywell's and other earth magnetic field sensing are Anisotropic Magnetoresistive sensors which only sense to ~100Gauss or 0.01T. However, they are generally more sensitive; 

For a sensor to work in the range you need (purple line below), Hall effect (cheap), Magneto-Optical (expensive) and Search coils will work for your application.

I did find one Giant Mageneto Resistive IC, the ACS70331, but it only works to 500 Gauss (0.05T)

I do also know that Hall effects work past the purple line in the graph (greater than 10T)