Magnetic proximity effect in thin films of Ni on nonmagnetic metals

The effect on the ferromagnetism of very thin films of Ni in contact with the nonferromagnetic metals Al, Au, Cr, and Mn was studied by spin-polarized tunneling measurements. For up to three atomic layers of Ni in contact with Al, the measured spin polarization $P$ of the tunneling electrons was zero, implying that the Ni was not ferromagnetic. This result agreed with our previous result for Ni on Al. On the other hand, for only one atomic layer of Ni in contact with Au, $P\simeq 4\%$; for two atomic layers $P\simeq 17\%$, which was 70% of the thick-film value. Two atomic layers of Ni on Mn or Cr showed very small ($P\simeq 1\%$), but finite, values of polarization. These results are compared with other experimental results and with theory and show generally good agreement.