#!/usr/bin/env python
# coding: utf-8

# # Both spatially and time varying field
# 
# When it is necessary to specify an external magnetic field which varies both in space and time, it can be done by:
# 
# - defining an external magnetic field using `discretisedfield.Field`
# - passing `wave` argument to `micromagneticmodel.Zeeman` term
# 
# For more details on time-varying fields, please refer to other tutorials. We start by defining a system object.

# In[1]:


import oommfc as mc
import discretisedfield as df
import micromagneticmodel as mm

region = df.Region(p1=(-50e-9, -50e-9, 0), p2=(50e-9, 50e-9, 10e-9))
mesh = df.Mesh(region=region, cell=(5e-9, 5e-9, 5e-9))

system = mm.System(name="space_time_varying_field")


# Now we can specify spatial and time varying field components. For the time-varying component, we choose a sine-wave with $5\,\text{GHz}$ frequency and no time shift.

# In[2]:


def Hspace(point):
    x, y, z = point
    if x**2 + y**2 < 20e-9**2:
        return (0, 0, 1e6)
    else:
        return (0, 0, 0)


H = df.Field(mesh, nvdim=3, value=Hspace)


# The spatial distribution of the field looks like:

# In[3]:


H.sel("z").mpl()


# In[4]:


system.energy = mm.Zeeman(H=H, func="sin", f=2e9, t0=0)
system.dynamics = mm.Precession(gamma0=mm.consts.gamma0) + mm.Damping(alpha=1e-5)

# create system with above geometry and initial magnetisation
system.m = df.Field(mesh, nvdim=3, value=(0, 0.1, 1), norm=1.1e6)


# Now, we can drive the system using `TimeDriver`.

# In[5]:


td = mc.TimeDriver()
td.drive(system, t=5e-9, n=500)


# We can have a look at the Zeeman energy.

# In[6]:


system.table.mpl(y=["E_zeeman"])