You cannot simply download AIX 7.2 like free software. You must have a valid commercial relationship with IBM. If you have that relationship, Passport Advantage is your only safe and legal source.
No. AIX 7.2 is a commercial operating system that requires a valid license and software maintenance agreement. Free downloads are not legally available from official sources. If you have not purchased an AIX license, you will be redirected to IBM ESS, where your entitlement status will be checked. download aix 7.2 iso image
AIX installation images are hosted on the portal. To access the download section of ESS: You cannot simply download AIX 7