Explanation of sensor sensitivity in unit/hertz
In order to specify the voltage noise independent of frequency, whether voltage, magnetic, or thermal in a measurement with a "normalized bandwidth"  we use root of mean squared (rms) values / root of bandwidth 


voltage noise has units of volts per root Hertz (V·Hz^-½) or uV/(Hz^½)
magnetic noise of Tesla per root Hertz (T·Hz^-½) or often pT/(Hz^½)
Below 1Hz does not apply as 1/f noise takes over.



  
  To read a value off this curve, you would choose a filter bandwidth (BW) about centre f and multiply the reading by BW^½. in Hz^½
  To measure a sample,  I think you would need to compute and apply a magnetic field  H(f) and measure the minimum detectable signal in Volts to make a SNR =1 or raise the noise voltage by 40% or *root(2) and filter the bandwidth again in Hz .  
  But not having done this before, I refer you to this.
  http://arjuna.ist.utl.pt/dissertacoes/entrega/teses/56087/Tese.pdf