Yes, you can use Sample Editors by other manufacturers. Most of them support the DirectX or VST Plug-In interface. Use the key command Start External Sample Editor. Alternatively, you can double-click the audio file while holding the Alt key in the arrange window. There are some restrictions:
 
Not every editor recognizes regions. So far, we've been testing CoolEdit and SoundForge.
 
You cannot work on split stereo files in external editors. The overview graphic won't be recreated automatically after an edit in an external editor. Select Audio File > Refresh Overview(s) after the edit. It is not possible to change the length of an audio file with an external sample editor, because Logic could no longer assign the edited region to the audio file. After the use of the key command Convert Regions Into Individual Audio Files, you can change the lengths of the new files individually with an external editor.