We are operating a high-frequency MFM (HF-MFM) setup in order to visualize the movement of magnetic domains and write fields of recording heads at high frequencies like 1-5 GHz. To do this, we need to prepare specific magnetic cantilevers, that is, we sputter a ferrite film on the micromachined silicon cantilevers as the magnetic active coating, see e.g. M. Kirsch et al, J. Vac. Sci. Technol. B 25(5), 1679 (2007). We had tested two types of ferrites as 20-nm thick coatings, (Ni,Zn)Fe2O4 and a Z-type hexaferrite Ba2Co3Fe24O41 (BCFO). The latter one proved to be better for the high frequencies.
Now, I would like to know what could be the best suited ferrite material for our purpose, and where can I find a target (5 cm dia.) for sputtering?
Relate to the target preparation, we normally use mechanical milling, of oxide powders with the correct stoichiometry, then we compress followed by a short sintering process, for 1h, where temperatures can vary from 900 to 1200 ºC
My comment is not an answer. Maybe you will use a magnetron sputtering system. How about confirming your sputtering system goes well or not by using a conductive saucer with 5cm diameter and fill the saucer with stoichiometric NiO, ZnO and Fe3Ox powders. Because ferrite targets may reduce magnetic field above the target, then, sputtering rates may be quite low.
Sion 's suggestion appears to weigh better in implementation. Trial and error will do the rest towards success!
Just thought about the thickness measurements for such films and what role it may play operationally at such high frequencies. We found that a Doubly oscillating quartz wafer , mutually decoupled pairs of electrodes deposited on the same wafer of quartz can play a role that helps generate ultra thin films accurately, down to few Angstroms!
ask Fabio Coccetti in LAAS Toulouse, he is working with a very good lab in Bordeaux called ICMCB where they are fabricating very high quality ferrite thin films featuring quality factor in the range of 30 up to 30 GHz
See M.Maglione in ICMCB Bordeaux or B.Viala in CEA-LETI grenoble
we had prepared cobalt ferrite and cobalt nickel ferrite targets using the method similar to sion (with slight modification to get 2 inch targets). Indeed it is difficult process and many trials are needed to optimize the structure. Another factor is that the magnetic behavior also behaves peculiarly when comparing powder and sputtered one. More work gives you the better result.
I guess you sputter on to some substrate (glass, alumina,...). Is the substrate heated while sputtering? Do you perform any post deposition annealing? all these will yield different results obviously. You need to check by XRD if the film is well crystallised.
The DQM quartz microbalance device will help quantify sputtering deposition thickness of different species in the ferrite sample under preparation as it eliminates the effect of change in frequencies due to pressure and temperature changes and isolates only the chnge that takes place due to only mass deposition!
Yes obviously we had maintained substrate temperature (by trail we had optimized) and also did post annealing. Our film crystallizes well with standard data for ferrites
Sridharan Ravi,
No compulsion to maintain substrate temperature control with DQM monitoing unless such a process treatment is desired by the nature of study being undertaken! Temperature and pressure changes in the local environment of the substrate are being taken care of DQM Quartz microbalance held i close proximity of substrate but still ensured to have mechanical and electrical decoupling.
Narendra Nath
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