Is there any reasonably inert magnetic oxide?

I spent yesterday evening looking for data on magnetic oxides. What is easily available isn't well organized, so I ask here in hope someone can remember.


I'm looking for a magnetic oxide (that is, an oxide that can be held in place by neodymium magnet in presence of liquid flow) that has magnetic properties at 350 Celsium and do not react with $\ce{H2S}+\ce{H2}+\ce{CO}$ mixture at this temperature at 50 bar. Common nonmagnetic oxides for this conditions are many $\ce{Al2O3, SiO2, TiO2,}$ to name a few. But with magnetic oxides I hit a wall.


Note: No, ferrites are not an option as they are easily reduced. Same with cobalt and nickel oxides. At first I looked at chromium and manganese componds, but compounds I checked lose magnetic ordering well below room temperature or are easily reduced.


Any suggestions?


Note: At the moment I'm researching compounds of chromium, manganese and middle rare earths, with little luck.


