Which Model Field to use in Django to store longitude and latitude values?

Use PointField to store lat long

p = Point(85.3240, 27.7172,srid=4326)

Django: 1.X:

https://docs.djangoproject.com/en/1.11/ref/contrib/gis/model-api/#pointfield

Django: 2.X:

https://docs.djangoproject.com/en/2.2/ref/contrib/gis/model-api/#pointfield

Django: 3.X: https://docs.djangoproject.com/en/3.0/ref/contrib/gis/model-api/#pointfield

Float is generally an approximation, see here for some simple examples. You could get very nice results modifying your model to something like DecimalField(max_digits=9, decimal_places=6), since decimals are very important in coordinates but using more than 6 is basically meaningless.