Magnetic anisotropy of Co-Cr thin films as a function of substrate temperature during deposition

A sequence of Co
78
Cr
22
films, 500 nm in thickness, was prepared by deposition on glass in a modified Varian D.C. magnetron S-gun sputtering system. The substrate temperature during deposition, T
s
, was fixed at various values with an upper limit of 300°C. Specimens were examined by VSM, TM, FMR and TEM. M
s
rises significantly with increasing T
s
, peaking at 200°C at 370 emu/cm
³
. The effective volume-averaged anisotropy drops for T
s
>110°C from +1.6 KOe to progressively negative values (-4.3 KOe at 300°C). From FMR we find indications of the presence, in addition to the transition and bulk layers, of a highly negative anisotropy constituent (
\sim-11.5
KOe anisotropy field). This resonance appears at T
s
values of 150°C and above. TEM plane and cross-section views taken on a T
s
= 150°C specimen show islands composed of tilted columns within the bulk. For vertical recording, specimens prepared at T
s
values between 50 and 100°C are recommended. On the other hand, for longitudinal recording applications, films prepared at T
s
values above 250°C would seem to be appropriate.