In Qur'an translations, we see that the phrase
right hands possess is used in many ayahs. What exactly does that phrase refer to?
It means a female slave. There is no need for marriage to her be Halal to her owner man. Buying her or receiving her as a share in Jihad spoil is enough that she be Halal to the man who poses her.
Before Islam, Arabs heavily had slavery culture but Islam had many rules about slaves but at the same time offered very high rewards for making them free. The Prophet and Ahl Bayt bought many slaves but made them free and many of them became best sahaba of the prophet and Ahl Bayt. In fact rules of Islam about slave are for control slavery and not for encouraging them. Also for some sins slaves must be freed so that the sin or mistake is forgiven. Islam encourage making the slaves free. Making slaves free is kind of punishment in Islam. If Islam wanted to oppose slavery strictly from first, Indeed tribal Arabs killed prophet and never accepted Islam. but Islam fought slavery step by step by controlling it.
The Quran clearly states that to be a Muslim one must not enslave one another.(Q 3:64).
Taking one another as lords in here is a kin to enslaving one another as arbaban would also have the notion of master/slave concept.
In order for one to be a mu'min (a faithful/believer) one must be a Muslim (in peace) first according to 49:14.
Then according to 23:1-6 a mu'min must have the following attributes
Hence, it would be contradictory to assume that ma malakat aymanahum (MMA) has the notion of slave as part of its meaning since that would violate the requirements of being a mu'min and hence being a Muslim also.
IMO the range of possible meaning to MMA cannot intersect the meaning of wives, otherwise it would be redundant to pair them in one verse.
So, one possible meaning of your right hands possesses/MMA would be whomever you have acquired their consent from. This would not violate the requirement of being a mu'min