Table 1 Results of hyperfine parameters as obtained in the precursor calcinated at different temperatures.

From: Atomic scale insights on the growth of BiFeO₃ nanoparticles

Sample	I	δ_i (mm/s)	Δ_i(mm/s)	Bⁱ_hf(Tesla)	f_i
Precursor	1	0.30 ± 0.03	0.35 ± 0.05	0	0.11
(a)	2	0.36 ± 0.01	0.76 ± 0.01	0	0.39
	3	0.30 ± 0.03	0.06 ± 0.05	4.11 ± 0.07	0.44
	4	0.03 ± 0.08	− 0.21 ± 0.15	12.27 ± 0.45	0.06
573 K 2 h	1	0.33 ± 0.04	0.40 ± 0.16	0	0.10
(b)	2	0.37 ± 0.04	0.84 ± 0.16	0	0.43
	3	0.28 ± 0.02	0.14 ± 0.03	4.34 ± 0.10	0.36
	4	0.32 ± 0.18	0.20 ± 0.33	11.44 ± 1.00	0.03
	5	0.42 ± 0.05	− 0.32 ± 0.11	48.40 ± 0.36	0.08
673 K 2 h	1	0.34 ± 0.01	0.49 ± 0.04	0	0.16
(c)	2	0.32 ± 0.01	0.94 ± 0.07	0	0.42
	3	0.32 ± 0.08	0.017 ± 0.12	4.24 ± 0.20	0.24
	4	0.32 ± 0.18	0.20 ± 0.33	11.44 ± 1.00	0.04
	5a	0.46 ± 0.04	0.53 ± 0.009	47.92 ± 0.31	0.05
	5b	0.40 ± 0.04	− 0.03 ± 0.09	48.60 ± 0.33	0.05
	6	0.22 ± 0.08	0.45 ± 0.15	43.02 ± 0.57	0.04
693 K 2 h	1	0.35 ± 0.01	0.51 ± 0.01	0	0.31
(d)	2	0.35 ± 0.01	1.04 ± 0.01	0	0.32
	3	0.12 ± 0.04	0.52 ± 0.07	5.24 ± 0.23	0.12
	4	0.40 ± 0.08	0.73 ± 0.25	11.11 ± 0.58	0.04
	5a	0.35 ± 0.03	− 0.23 ± 0.07	48.49 ± 0.26	0.09
	5b	0.41 ± 0.04	0.31 ± 0.09	48.81 ± 0.27	0.08
	6	0.40 ± 0.07	0.10 ± 0.14	39.26 ± 0.43	0.04
708 K 2 h	1	0.33 ± 0.04	0.26 ± 0.07	0	0.06
(e)	2	0.35 ± 0.01	0.78 ± 0.02	0	0.20
	3	0.43 ± 0.03	0.18 ± 0.05	6.25 ± 0.19	0.11
	4	0.47 ± 0.11	− 0.01 ± 0.22	19.67 ± 0.70	0.04
	5a	0.36 ± 0.01	− 0.16 ± 0.06	48.83 ± 0.14	0.29
	5b	0.37 ± 0.01	0.32 ± 0.06	49.41 ± 0.14	0.26
	6	0.32 ± 0.09	0.51 ± 0.19	41.75 ± 0.64	0.04
723 K 2 h	1a	0.35 ± 0.01	0.46 ± 0.02	0	0.11
(f)	5a	0.38 ± 0.007	− 0.11 ± 0.01	48.91 ± 0.04	0.45
	5b	0.40 ± 0.009	0.35 ± 0.02	49.16 ± 0.0	0.38
	6	0.36 ± 0.04	− 0.19 ± 0.09	42.06 ± 0.32	0.06
723 K 2 h	1a	0.29 ± 0.02	0.34 ± 0.02	0	0.12
Bext = 0.3 T	5a	0.39 ± 0.007	− 0.17 ± 0.01	48.98 ± 0.04	0.43
(g)	5b	0.41 ± 0.009	0.28 ± 0.02	49.3 ± 0.06	0.38
(g)	6	0.35 ± 0.03	0.2 ± 0.09	43.8 ± 0.32	0.07
773 K 2 h	1a	0.39 ± 0.04	0.49 ± 0.08	0	0.04
(h)	5a	0.38 ± 0.01	− 0.10 ± 0.01	49.40 ± 0.04	0.46
	5b	0.40 ± 0.01	0.33 ± 0.01	49.74 ± 0.03	0.46
	6	0.32 ± 0.04	0.58 ± 0.09	43.80 ± 0.34	0.04
773 K 2 h	1a	0.40 ± 0.02	0.50 ± 0.04	0	0.05
Bext = 0.3 T	5a	0.38 ± 0.004	− 0.12 ± 0.009	49.43 ± 0.02	0.45
(l)	5b	0.40 ± 0.004	0.31 ± 0.01	49.77 ± 0.03	0.46
(l)	6	0.24 ± 0.03	− 0.32 ± 0.06	44.10 ± 0.22	0.04
873 K 2 h	7	0.25 ± 0.01	0.57 ± 0.03	0	0.07
(j)	5a	0.39 ± 0.005	− 0.12 ± 0.01	49.49 ± 0.03	0.41
	5b	0.40 ± 0.004	0.33 ± 0.01	49.82 ± 0.03	0.49
	6	0.39 ± 0.06	0.74 ± 0.12	41.53 ± 0.42	0.03

f₁ and f₂ are due to relative fractions of iron atoms associated with nanoparticles of Bi₂₅FeO₄₀ and superparamagnetic particles (SPM) of BiFeO₃ and α-Fe₂O₃. f₃ is the fraction of iron atoms associated with nanoparticles of BiFeO₃ with size larger than the SPM limit and much lesser than that of bulk BiFeO₃ as deduced based on the hyperfine parameters. f₄ is the fraction of iron atoms associated with BiFeO₃ particles of size larger than that of f₃. f_5a,f_5b are the fractions of iron atoms associated with that of bulk BiFeO₃ particles, while f₆ is interpreted to be due to iron atoms associated with shell with core as BiFeO₃. In the case of precursor annealed at 873 K and beyond the fraction f₇ is attributed to Fe atoms associated with the shell of Bi₂₅FeO₄₀ formed at the surface of large sized BiFeO₃.

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Table 1 Results of hyperfine parameters as obtained in the precursor calcinated at different temperatures.

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