diff --git a/src/nqr_blochsimulator/classes/sample.py b/src/nqr_blochsimulator/classes/sample.py
index 9c59d93..fce067f 100644
--- a/src/nqr_blochsimulator/classes/sample.py
+++ b/src/nqr_blochsimulator/classes/sample.py
@@ -13,17 +13,18 @@ class Sample:
     def __init__(
         self,
         name : str,
-        density : float,
-        molar_mass : float,
+        atoms : float,
         resonant_frequency : float,
         gamma : float,
-        nuclear_spin : float,
+        nuclear_spin : str,
         spin_factor : float,
         powder_factor : float,
         filling_factor : float,
         T1 : float,
         T2 : float,
         T2_star : float,
+        density : float,
+        molar_mass : float,
         atom_density=None,
         sample_volume=None,
         sample_length=None,
@@ -36,16 +37,14 @@ class Sample:
         ----------
             name : str
                 The name of the sample.
-            density : float
-                The density of the sample (g/m^3 or kg/m^3).
-            molar_mass : float
-                The molar mass of the sample (g/mol or kg/mol).
+            atoms : float
+                The number of atoms in the sample.
             resonant_frequency : float
                 The resonant frequency of the sample in MHz.
             gamma : float
                 The gamma value of the sample in MHz/T.
-            nuclear_spin : float
-                The nuclear spin quantum number of the sample.
+            nuclear_spin : string
+                The nuclear spin quantum number of the sample. Can be half-integer spin.
             spin_factor : float
                 The spin transition factor of the sample.
             powder_factor : float
@@ -58,6 +57,10 @@ class Sample:
                 The spin-spin relaxation time of the sample in microseconds.
             T2_star : float
                 The effective spin-spin relaxation time of the sample in microseconds.
+            density : float
+                The density of the sample (g/m^3 or kg/m^3).
+            molar_mass : float
+                The molar mass of the sample (g/mol or kg/mol).
             atom_density : float, optional
                 The atom density of the sample (atoms per cm^3). By default None.
             sample_volume : float, optional
@@ -68,6 +71,7 @@ class Sample:
                 The diameter of the sample m(m). By default None.
         """
         self.name = name
+        self.atoms = atoms
         self.density = density
         self.molar_mass = molar_mass
         self.resonant_frequency = resonant_frequency * 1e6
@@ -83,7 +87,10 @@ class Sample:
         self.sample_volume = sample_volume
         self.sample_length = sample_length
         self.sample_diameter = sample_diameter
-        self.calculate_atoms()
+        if self.atoms == 0:
+            self.calculate_atoms()
+
+    # These are helper methods that are used to calculate different parameters of the sample.
 
     def calculate_atoms(self):
         """
@@ -103,6 +110,8 @@ class Sample:
         else:
             self.atoms = self.avogadro * self.density / self.molar_mass
 
+        logger.debug(f"Number of atoms in the sample: {self.atoms}")
+
     def pauli_spin_matrices(self, spin):
         """
         Generate the spin matrices for a given spin value.
diff --git a/src/nqr_blochsimulator/classes/simulation.py b/src/nqr_blochsimulator/classes/simulation.py
index 21ea5cd..3ea0f26 100644
--- a/src/nqr_blochsimulator/classes/simulation.py
+++ b/src/nqr_blochsimulator/classes/simulation.py
@@ -313,10 +313,13 @@ class Simulation:
         """
         u = 4 * np.pi * 1e-7  # permeability of free space
 
+        num, den = self.sample.nuclear_spin.split("/")
+        nuclear_spin = float(num) / float(den)
+
         magnetization = (
             (
                 (self.sample.gamma * 2 * self.sample.atoms)
-                / (2 * self.sample.nuclear_spin + 1)
+                / (2 * nuclear_spin + 1)
             )
             * (h**2 * self.sample.resonant_frequency)
             / (Boltzmann * self.temperature)
diff --git a/tests/simulation.py b/tests/simulation.py
index 77b5a7d..fe56bc7 100644
--- a/tests/simulation.py
+++ b/tests/simulation.py
@@ -13,11 +13,12 @@ class TestSimulation(unittest.TestCase):
     def setUp(self):
         self.sample = Sample(
             "BiPh3",
+            atoms=0,
             density=1.585e6,  # g/m^3
             molar_mass=440.3,  # g/mol
             resonant_frequency=83.56e6,  # Hz
             gamma=43.42,  # MHz/T
-            nuclear_spin= 9 / 2,
+            nuclear_spin= "9/2",
             spin_factor=1.94
             powder_factor=0.75,
             filling_factor=0.7,