I'm not sure what you want AIX for, but a brief look at the Wikipedia article indicates that, in addition to version (v3) that ran natively on PowerPC systems I knew of, AIXv2 has run on ROMP, 386, and s/370 (& s/390) using a microkernel -- it'd be necessary to emulate the processor and entire system, or to emulate the software and provide a compatibility layer in place of the microkernel (which handled all I/O), which might get better performance.

The easiest option is probably using pearpc to run AIXv3, but it won't go very well at all.

Do you have some specific AIX binaries you need to run, or what? You've already got a UNIX, so "emulating AIX" is nearly taken care of; you'd need the source to port any programs to AIX on ARM, too.