1. High powered PEMF seems to be very fast with positive outcomes and seems to have a lasting effect.
The input signal is a impulse. Frequency 1-10 Hz seems to be good.
That's the Standard.
If you generate a magnetic field and it collapses then you will get more energy out of the collapsing magnetic field that you are inputting. (There should be a video on YouTube about this...)
So you will get back every time a RE-EMF from the coil. And the connected amplifier has to take the RE-EMF.
If the signal is NOT a sinus signal, then the form of the input signal will be distorted through the RE-EMF pulse that will came from the coil.
So the RE-EMF is a problem in electronics if you want to drive a coil.
(Except someone want to build a overunity device.)
2. Here is the waveform as requested.
Sine Ramped Triangle Waveform
3. Here are another two similar types of Waveforms.
Sine Phi Ramped Triangle & Sine Phi Reverse Ramped Triangle Waveforms
For more details, please check the link: