We know your iPhone comes with Voice Memos, but if you want a more powerful audio recorder, the Recordium Mini may be a better option.
Recordium Mini is a powerful and easy-to-use audio recording app for iPhone and iPad. The iOS app features elegant and simple iOS 7-styled user interface and supports 4 different recording formats and 3 adjustable sample rates to manage the size and quality of your recording, and you can highlight important parts of the track while recording or during playback. Moreover, the audio recorder also features many useful recording functions such as interruption protection, enhanced recording volume, auto save, and etc. apart from that, the audio recorder supports iCloud and allows you to wirelessly transmit audio files via WiFi.
Recordium Mini is available for free at present. If you need it, head to App Store for download.