PRESSURE-INDUCED FERROMAGNETIC STATES IN SR14MNAS11

Measurements of the temperature dependence of the magnetic susceptibility of Sr14MnAs11 were made from ambient pressure to P less-than-or-equal-to 20 kbars. At ambient pressure this compound is known to be a semiconductor with a Curie susceptibility down to as low as 5 K. It is found that raising the pressure to 7 kbars enhances the susceptibility somewhat and that at pressures above 10-11 kbars the susceptibility is enhanced by more than an order of magnitude and an ordered magnetic state occurs with a transition temperature that increases as the pressure is increased. This suggests that the applied pressure leads to a band-crossing transition from semiconductor to metal and a consequent exchange coupling of the Mn spins.