The liquid surface will be disturbed at lower values of magnetic force.  When sufficient magnetic field is applied, it is possible that the bubble can detach from the surface. The influence of temperature has to be looked into.  It is a good area for research. 

But it seems coagulation of nano particles will be predominant due to magnetic forces and will create problem for existence of nano fluid itself. Magnetic forces will not differentiate vapor and liquid. can there be some vapor forming / assisting ferrous nano particles?

You may try with para magnetic or dia-magnetic nano particles dispersed in EG+water mixture or some other base liquid for stability.  A strong magnetic field is required which has the requisite force to move the particles.  It requires certain trails and experienced technicians for fabrication.  Further, when the liquid is at a higher temperature the boiling process should sustain.  These are certain challenges to be faced before it is successful.  You need not consider  ferro magnetic material as it might get lead to coagulation.  

Boiling of ferrofluids is well-known problem. See, for example, http://www.academia.edu/download/8812393/jmmm_2004.pdf and [12], [13] in this paper. The main problem is the shape of the bubble in the magnetic field, not problem of particles coagulation.

Or this paper http://link.springer.com/article/10.1007/s00231-004-0529-1

If you want to boil magnetic fluid in zero gravity it necessary to have magnetic field with the gradient oriented to the solid surface of the heat exchanger. In the field of ordinary small permanent magnet  in the magnetic fluid with magnetization about 30 kA/m volume force acting on the bubble will be comparable with gravity force and you will have the same effect as in the gravity.