I have extensively used PLD for magnetic thin film deposition. For dielectric measurements, you need to use sandwiched structure (your films between two conducting electrodes), so substrate is not very important. The magnetic contribution from your substrate could be a problem if your film is not very magnetic. Single crystal of Al2O3 as substrate could be appropriate for such measurements. But you need to subtract the diamagnetic contribution of substrate from your measurements. For this, you should run the magnetic measurements of Al2O3 without any film. And then with your film deposited on it.    

Most perovskite oxide thin films by PLD are grow at very high temperatures, especially epitaxial thin films. Therefore you need an epitaxially matched substrate, and on such a  substrate you need specially conducting oxide thin films (LaNiO3, SrRuO3.

Now if want study both the magnetic and dielectric properties, you should therefore be extra cautious in selecting non magnetic (substrate and electrode layers) to study the magnetic and dielectric properties of  PLD grown oxide films.

K. Sreenivas

I used Pt/Si wafers, a common silicon wafer with an additional layer of Pt in on  of the faces. Quartz coated with gold layer is another option.  Also, if the processing of the coating allows it, you can used also FTO or ITO ( temperature lower than 600ºC).

Depending on the lattice structure and parameter you may use Noble metal coated substrates for best measurements. All the suggested substrates are highly reliable however can cause directional growth and undesired crystal structures.

If you want to avoid grain boundary effects, you should choose a perovskite substrate closely lattice-matched to your film.  Crystec GmbH is an excellent supplier.  See Fig. 9 of the linked paper, below, to select an appropriate substrate: 

https://www.researchgate.net/publication/227540551_A_Thin_Film_Approach_to_Engineering_Functionality_into_Oxides

Article A Thin Film Approach to Engineering Functionality Into Oxides

Dear Sir,

I think the best substrate for thin film permeability and permittivity is a nonmagnetic and nondielectric substrate.

At my opinion a amorph glass or crystal glas substrate or a nonmagnetic metal substrate .

Yours Sincerely

F. Gräbner