Follow TV Tropes
Arguably neither artifacts from Mahou Sensei Negima are true invisibility cloaks.
Kaedes artifact, Tengu no Kakuremino, is something more of a hyperspace/dimensional portal. It may actually be a form of teleportation in the Magic World as it was canceled by CoLM, in which case it would simply imply a relocate spell from the "storage place" of the cloak to the current location.
Natsumis artifact, Adiutor Solitarius, is more of a Somebody Else's Problem field as they are not trully invisible, just unnoticeable(I wonder if a video camera would negate it's effect, or if the effect would spread to the image on the screen, like in one of those optical ilusion pictures where you simply don't notice part of the content).
For refference: 
Arguably both are more awesome than a simple invisibility cloak, as Chisame explains above for the second artifact.
This troper is not sure if this should be removed.
Camoflage — not an invisibility cloak.
There are also the elven cloaks given to the members of the Fellowship. They don't actually turn the character invisible; instead, they meld with the surroundings in an inconspicuous way (e.g. the cloak becomes a stone in rocky terrain).
Not an exmaple - Somebody Else's Problem
Does not turn people invisible — not an example.
Community Showcase More
How well does it match the trope?