Try this way,
instead of this line
alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP,
SystemClock.elapsedRealtime()+60000,PERIOD,pi);
try my logic,
alarmManager.set(AlarmManager.RTC_WAKEUP, 60 * 1000, pi);
You can also see a very good example of AlarmManager.