The Effect of B Doping on the Martensitic Transitions, Magnetocaloric and Magnetic Properties in Ni $_{48}$Mn $_{39}$In $_{13-{\rm x}}$B $_{\rm x}$ Ribbons

The influence of boron substitution for indium on phase transformation, magnetocaloric and exchange bias (EB) properties in annealed Ni
₄₈
Mn
₃₉
In
_13
-
x
B
_x
(
x
= 1-4) ribbons has been investigated. It is observed that an increase in B concentration strongly affects the magnetic state of the martensitic phase, the magnetic entropy change and the EB properties of the ribbons. These ribbons crystallize in a partially ordered B2 phase structure. The martensitic structural transition temperature (
T
_M
) decreases from 270 K for
x
= 0 to 175 K for
x
= 2 with increasing B content. A further increase in B content results in an increase of
T
_M
to 268 K for
x
= 4. The peak value of positive magnetic entropy change (Δ
S
_M
) decreases from 20.2 J/kg K for
x
= 0 to 2.8 J/kg K for
x
= 4 for a magnetic field change
H
= 50 kOe. The values of exchange bias field (
H
_E
) and the coercivity (
H
_C
) change from 258 Oe and 192 Oe to 397 Oe and 600 Oe, respectively, as x is increased from 0 to 4. The phenomena are attributed to the change of exchange interactions in B-substituted Ni-Mn-In ribbons due to the change of distance between Mn atoms.