High spin state of Mn in an ideal monolayer on Ag(001)

We studied the magnetic properties of ultra-thin Mn films deposited on Ag ( 001) held at 80 K with soft; X-ray absorption and magnetic circular dichroi sm. The observed shape and branching ratio of the Mn 2p absorption edge as a function of Mn coverage demonstrate that, up to similar to 0.9 ML, the Mn adopts a stable high spin state similar to the Mn atom Hund's rule S-6(5/2 ) ground state. Above this coverage a rapid transition from localized high spin to itinerant low spin behavior of the Mn 3d electrons is evidenced. Ma gnetic circular dichroism shows no sign of long range ferromagnetic order i n these films at 80 K. The data, first confirm the large atomic-like local magnetic moment, and second are in line with the in-plane c(2 x 2) antiferr omagnetic order, reported recently (Phys. Rev. B 57, 1141 (1998)), for Mn i n the nearly ideal on-top Mn monolayer formed by 0.9 ML deposited at 80 K.