With custom click action, using $ionicNavBarDelegate:
<button class="button" ng-click="goBack()">Back</button>
function MyCtrl($scope, $ionicNavBarDelegate) {
$scope.goBack = function() {
$ionicNavBarDelegate.back();
};
}
From the ionic docs: http://ionicframework.com/docs/nightly/api/directive/ionNavBackButton/