  The experimentally observed ferromagnetism in MgB2 in the normal state is
attributed to micro phase separated inclusions of iron. This magnetic character
is also observed when the iron content of the samples is reduced below 20
micro-g/g, however in these samples the diamagnetism of MgB2 is apparent and is
measured. It is found experimentally that the diamagnetic susceptibility at
room temperature of B element, MgB2 and MgB4 is close to the ratio 1:2:4,
suggesting that the diamagnetism in these borides is confined to the boron
atoms. This observation supports a picture in which the two electrons of Mg are
donated to B in MgB2
