mnemonic vs mnemotechnic

mnemonic is a noun but mnemotechnic is not a noun.

Word	Noun	Adjective	Verb	Adverb
mnemonic	Yes	Yes	No	No
mnemotechnic	No	Yes	No	No

As adjectives, mnemonic and mnemotechnic are synonyms defined as:

mnemonic and mnemotechnic: of or relating to or involved the practice of aiding the memory

Other synonyms of mnemonic include mnemotechnical.

mnemonic (noun)	mnemotechnic (noun)
a device (such as a rhyme or acronym) used to aid recall

mnemonic (adjective)	mnemotechnic (adjective)
of or relating to or involved the practice of aiding the memory	of or relating to or involved the practice of aiding the memory