NMR measurements on obliquely evaporated Co-Cr films

Abstract

The distribution of the hyperfine fields or the resonance frequencies in metals and alloys obtained by NMR measurements have been known for a long time. Recently, new experimental data have been published about thin films for studying their chemical inhomogeneities. An example is the study on sputtered and evaporated Co-Cr layers. In this paper we report on the compositional distribution of co-evaporated Co-Cr films by using the Co spin-echo NMR technique. For comparison single source evaporated samples of Co-Cr and pure Co as well as two alloyed ribbons ("bulk" samples) have also been measured. Based on the NMR results the local Cr concentration of the ferromagnetic and less ferromagnetic regions are determined. In comparison the data from the co-evaporated films, even at low substrate temperature, have clearly shown the presence of a process-induced compositional separation. This is in qualitative agreement with the magnetic properties of the samples.

Tailoring growth and local composition by oblique-incidence deposition: a review and new experimental data

“…Again the main line is due to a highly pure Co component. The first satellite peak is due to an amount of Co surrounded by one Cr nearest neighbour [104][105][106]. The appearance of a strong main line and the first satellite peak justify the conclusion that in this sample compositional separation has obviously occurred, and that highly pure CO regions are present.…”

“…46 for comparison. According to NMR measurements [106] these ribbons are in a more homogeneous state than the CoCr powder samples. The model lines are for random distributions of Co and Cr and no Cr-Cr bonds, according to models from Haines [115] and Fartash et al [116].…”

“…. Spin-echo spectrum of obliquely co-evaporated T R films from the S series: $910506E (Cos2Crls, h ~227 nm) [106].…”

‘Giant’ magnetoresistance in obliquely co-evaporated Co-Ag films

“…This has also been confirmed by NMR' experiments. By preliminary NMR experiments we have shown that, for (Co-Cr and Co-Ag) films deposited at room temperature, the number of Co-Co clusters has increased after an annealing treatment is carried out [16,17]. After annealing, an hcp Co structure is present.…”

“…The results presented in this paper are based on a systematic research on obliquely (co-Ievaporated Co-Cr media for magnetic recording applications. The relations between deposition parameters, morphology, texture and magnetic behaviour of this type of thin film have been studied in our group in the past 5 years [6][7][8]11,12,17,19]. From this study we learned, from experimental data obtained by various methods and techniques, that in the case of Co-Cr even at ambient temperature a compositional separation takes place.…”