FMR field sweep for Synthetic Antiferromagnet (SAF) system

[Mohit Mithaliya]

Hello Serban, 
                          I was working on FMR simulation on Boris and i have performed simulation for permalloy with the given code in Boris data. But now i want to perform the FMR for the Synthetic antiferromagnet (SAF) system. Since last week i was developing a code for SAF FMR, but i am having difficulty getting FMR. please check the and help,  
In code, there are several issues:   1= it is not saving Hbias in the saved file. 
Please, sir, check this code and help. Thank you
                                                             


import sys
import matplotlib.pyplot as plt
import numpy as np

# Setup Boris NetSocks
sys.path.append(r"D:\\Boris Data\\BorisPythonScripts")
from NetSocks import NSClient, customize_plots

ns = NSClient()
ns.configure(True)
customize_plots()

# ==================== SMART LOAD FUNCTION =========================
def smart_loadtxt(filename):
    with open(filename) as f:
        for i, line in enumerate(f):
            try:
                float(line.strip().split()[0])  # try to convert first value to float
                break
            except:
                continue
    return np.loadtxt(filename, skiprows=i)

# =========================== SAF SETUP ============================
def SetupSAF():
    ns.reset()

    FM1 = ns.Ferromagnet([200e-9, 200e-9, 2e-9], [5e-9, 5e-9, 1e-9])
    FM1.modules(['Zeeman', 'demag', 'exchange', 'surfexchange'])
    FM1.param.K1 = 1e-3
    FM1.param.ea1 = [1, 0, 0]
    FM1.param.grel = 1
    FM1.param.A = 13e-12
    FM1.param.J1 = -20e-6

    FM2 = ns.Ferromagnet([0.0, 0.0, 3e-9, 200e-9, 200e-9, 6e-9], [5e-9, 5e-9, 1e-9])
    FM2.modules(['Zeeman', 'demag', 'exchange', 'surfexchange'])
    FM2.param.K1 = 1e-3
    FM2.param.ea1 = [1, 0, 0]
    FM2.param.grel = 1
    FM2.param.A = 13e-12
    FM2.param.J1 = -20e-6

    ns.addmodule('supermesh', 'sdemag')
    ns.savesim('fmr')

# ==================== PREPARE FMR SIMULATION ======================
def PrepareFMRSimulation(simulationFile):
    ns.loadsim(simulationFile)
    ns.savedatafile('fmrcycle.txt')

    ns.setstage('Hfmr', 'FM1')
    ns.addstage('Hfmr', 'FM1')
    ns.editdatasave(1, 'step')

    # Apply field and collect data from both FM1 and FM2
    ns.setdata('Ha', 'FM1')
    ns.setdata('Ha', 'FM2')
    ns.adddata('<M>', 'FM1')  # columns 3–5
    ns.adddata('<M>', 'FM2')  # columns 6–8

    ns.setangle(90, 0)
    ns.savesim(simulationFile)

# ==================== SAF FMR SWEEP FUNCTION ======================
def RunFMRStep(biasH, rfFreq, fileName):
    cyclesMax = 200
    cyclesChunk = 5
    rfH = 100
    steps_per_cycle = 5
    stopping_time = (1 / rfFreq) / steps_per_cycle

    previous_amplitude = 0.0
    cyclesSimulated = 0

    while cyclesSimulated < cyclesMax:
        ns.reset()
        ns.dp_clearall()

        ns.editstagevalue(0, [0, biasH, 0, rfH, 0, 0, steps_per_cycle, cyclesChunk])
        ns.editstagestop(0, 'time', stopping_time)
        ns.editstagevalue(1, [0, biasH, 0, rfH, 0, 0, steps_per_cycle, 1])
        ns.editstagestop(1, 'time', stopping_time)

        ns.Run()

        try:
            data = smart_loadtxt('fmrcycle.txt')
            Mx1 = data[:, 3]
            Mx2 = data[:, 6]
            netMx = (2/5) * Mx1 + (3/5) * Mx2
            time = data[:, 0]

            processed = np.column_stack((netMx, time))
            np.savetxt('netmx_vs_time.txt', processed, fmt='%.6e')

            ns.dp_load('netmx_vs_time.txt', [0, 1])
            new_amplitude = float(ns.dp_getampli(0, steps_per_cycle))
        except Exception as e:
            print("⚠️ Error loading or processing fmrcycle.txt:", e)
            new_amplitude = 0.0

        cyclesSimulated += cyclesChunk

        if new_amplitude:
            change = abs((new_amplitude - previous_amplitude) / new_amplitude)
            if change < 0.001:
                break
        previous_amplitude = new_amplitude

    ns.SaveDataToFile(fileName, [abs(biasH), new_amplitude])

# =========================== MAIN SCRIPT ===========================
simulation_file = 'fmr'
output_file = simulation_file + '_fieldsweepFMR_data.txt'
ns.dp_newfile(output_file)

Hstart = 75e3
Hend = 85e3
Hstep = 1000
rfFreq = 9e9

SetupSAF()
PrepareFMRSimulation(simulation_file)

for step in range(int((Hend - Hstart) / Hstep) + 1):
    Hbias = Hstart + step * Hstep
    print("Bias field =", Hbias)
    RunFMRStep(-Hbias, rfFreq, output_file)

# ============================ PLOTTING =============================
data = ns.Get_Data_Columns(output_file, [0, 1])
Hrange = [H for H in data[0]]
fmr_signal = [amplitude**2 for amplitude in data[1]]

plt.figure()
plt.axes(xlabel='H (kA/m)', ylabel='FMR Signal (a.u.)')
plt.plot(np.array(Hrange) / 1e3, fmr_signal, 'o-', label='Net SAF Mx')
plt.legend()
plt.savefig('SAF_FMR_NET.png')
plt.show()