Tuning exchange bias by Co doping in Mn50Ni41-xSn9Cox melt-spun ribbons
D. W. Zhao, G. K. Li, S. Q. Wang, L. Maa), C. M. Zhen, and D. L. Hou
Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University,
Shijiazhuang 050024, China
W. H. Wang, E. K. Liu, J. L. Chen, and G. H. Wu
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese
Academy of Sciences, Beijing 100190, China
Supplementary information:
1) The structure of the Mn50Ni41-xSn9Cox ribbons.
FIG. S1. XRD patterns for Mn50Ni41-xSn9Cox (x=0, 1, 2, 3, 4, 5, 6).
Fig. S1 shows the room temperature XRD patterns for the Mn50Ni41-xSn9Cox ribbons. It can be
seen that the Co0 sample has a tetragonal martensitic structure with lattice parameters a=b=5.570 Å
and c=6.851 Å. After doping Co into the alloy, the Co1~Co6 samples all show B2 structure with
order-independent principle reflections for the (220), (400) and (422) planes and an order-dependent
a)
Author to whom correspondence should be addressed.
Electronic mail: majimei@126.com
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superlattice reflection for the (200) plane. The values of the lattice parameters for the Co1~Co6
samples are listed in Fig. S1. This indicates that doping with Co does not change the crystal
structure of MnNiSn. Due to the fact that the martensitic transformation temperature for the Co0
(Co1) sample lies near room temperature, the Co0 (Co1) sample also shows some austenitic
(martensitic) structure peaks (marked by asterisks).
2) The Co concentration dependence of the blocking temperature, Tf, the
martensitic transformation temperature, TM, and Curie temperature, TC, of
Mn50Ni41-xSn9Cox (x= 0, 1, 2, 3, 4, 5) ribbons.
As listed in Table S1, the partial substitution of Co for Ni in the given composition range leads
to a lowered martensitic transformation temperature (TM), from 300 K to 145 K, and an increased
Curie temperature (TC), from 285 K to 400 K.
The increase in TC results from the fact that the magnetic interaction between Co and Mn
atoms is stronger than that between Ni and Mn atoms. The decrease in TM is attributed to the
decrease in the valence electron concentration e/a.
Table S1. Blocking temperatures with f=10.0 Hz, Tf, martensitic transformation temperatures, TM, and Curie
temperatures, TC, of Mn50Ni41-xSn9Cox (x= 0, 1, 2, 3, 4, 5) ribbons.
x (at.%)
0
1
2
3
4
5
Tf (K)
135
114
121
129
142
--
TM (K)
300
295
276
237
233
145
TC (K)
285
300
320
345
373
400
3) Details on the method used to obtain the value of P.
In the following, the Mn50Ni40Sn9Co1 sample is used as an example of how we obtained the
value of P. First, the temperatures at the peaks of the χ′ (T) curves for the Mn50Ni40Sn9Co1 sample
were defined as Tf(i) (i=1-6) and the corresponding six frequencies were determined as ω(i) (i=1-6).
T f ( i  1)  T f ( i )
See Table S2. Second, according to P ( i )  T ( i )log  ( i  1)  log  ( i ) (i=1-5), five different
f
10
10
2
5
values of P were obtained. Third, the average value of P was obtained according to P

 P (i )
i 1
5
.
Finally, we got the value of P for the Mn50Ni40Sn9Co1 sample as follows: P  P  P , where P is
the standard error.
Table S2. Angular frequencies, ω(i), blocking temperatures with different frequencies, Tf(i), and the values of P
for the Mn50Ni40Sn9Co1 sample.
i
ω(i) (rad/s)
Tf(i) (K)
P(i)
1
62.83
114.0
0.0239
2
154.57
115.0
0.0197
3
380.13
116.0
0.0221
0.0220±
4
934.94
117.0
0.0221
0.0013
5
2299.65
117.9
0.0224
6
5654.87
119.0
--
P
4) Discussion regarding the Mn50Ni35Sn9Co6 sample.
Fig. S2 shows the temperature dependence of the magnetization for the Mn50Ni35Sn9Co6
sample under a magnetic field of 500 Oe. The martensitic transformation is not observed in the
sample, i.e., it maintains the parent phase down to as low as 10 K. The magnetic hysteresis loop for
the Mn50Ni35Sn9Co6 sample measured at 10 K after 500 Oe field cooling is shown in the inset of Fig.
S1. It can be seen that the sample shows typical ferromagnetic behavior. Furthermore, the exchange
bias effect was not observed, and the sample saturation magnetization (MS=125 emu/g) was much
larger than that for any of the Mn50Ni41-xSn9Cox (x=0-5) alloys. All the phenomena observed for the
Mn50Ni35Sn9Co6 sample result from the fact that it maintains the parent phase down to 10 K.
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FIG. S2. Temperature dependence of magnetization for the Mn50Ni35Sn9Co6 sample under a magnetic field of 500
Oe. The inset is the magnetic hysteresis loop for the Mn50Ni35Sn9Co6 sample measured at 10 K after 500 Oe field
cooling.
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